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Finderscope Webcam

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Finderscope Webcam

I have been giving some help to a former school-friend who has fairly recently taken up observational astronomy. One of his major problems has been star hopping. He prefers to locate a target manually, rather than by GOTO methods, but has been frequently thwarted by the numerous difficulties encountered. A significant one of these has been an inability to accurately determine exactly which starfield he is looking at because of the limited light-gathering capacity of his finder. This has required him to take images using a webcam with his main OTA and (hopefully!) use these to determine his viewpoint, but his ability to do so is severely constrained by the limited field-of-view of this setup.

Being a practical person, he has developed what seems to be a simple yet inventive solution, which can best be described as a Finderscope Webcam. In other words, a webcam mounted on a finder, imaging the scene afocally. This has the double advantage of greater sensitivity while retaining the wider field-of-view. Whilst currently a rather "DIY" device, it uses easily available components combined in a rather novel arrangement and so should not be difficult to replicate.

I have seen promising results from it and so feel a device such as this could be of value to other observers, as it does have a number of additional advantages over a standard "optical" finder:-

1) The device can be rotated (manually) and the image flipped (using the driver program) so that the view given by the webcam finder matches any "planetarium program" view that the observer might be using to verify that the hopping sequence is being carried out correctly
2) The "ergonomics" of the device are much superior to that of an optical finder. Specifically, because the observer does not have to look through the device there is no need to adopt uncomfortable postures at the telescope and no problems are caused for spectacle wearers
3) The observer can record both the hopping sequence taken and images of interest found during the "hop", both for later analysis
4) By use of suitable driver software, it would seem possible to apply "dark frame correction" and live stacking to the image stream. Both of these techniques would significantly increase the image quality compared to an optical finder

I was thus wondering if any member knows whether a similar device is already available or has contacts with manufacturers of telescope accessories who might be interested in developing & marketing such a device?

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Something like this.
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Similar set up

A web-cam on the finder is a useful arrangement.  Since i already have a  9x50 finder and a suitable camera, i bought one of these from FLO:  https://www.firstlightoptics.com/adapters/astro-essentials-sky-watcher-9....
Agreed, Its helpfull to have some form of dark frame subtraction to remove hot-pixels if the web-cam is used with longer exposure settings.   False stars can be confused with real ones ! 

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Meccano and Jubilee clips

Here is my DIY version using Meccano and Jubilee clips used as an electronic finder on my remote setup. I don't find it that sensitive though with the old webcam I am using, perhaps mag 4-5. (Maybe more modern webcams are better) Good enough to put a bright star in the main camera field to do a local sync of the goto though.

Cheers

Robin

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Finderscope webcam

Thanks for those comments. However, between them they do rather illustrate the problems with "standard" solutions which my friend Roger was trying to solve. In the case of the Evoguide 50ED plus ZWO camera bundle, the most obvious objection is cost! (£319, even as a "special offer"). While I'm sure there must be a market for such a device at this price point among "professional amateurs", I rather doubt whether many casual backgarden skywatchers would be willing to invest this amount, possibly more than their entire setup has cost them so far, in order to obtain one. This is further compounded by the fact that this device does not seem to be able to make up its mind as to what it is. For example, a "webcam finderscope" does not need the ability to accept different cameras/eyepieces nor does it need to be able to alter the focus: once the selected webcam is in the correct position it should not need to be altered or adjusted thereafter. Also, does a finder for a "moderate" telescope really need a 50mm "Ohara ED doublet objective that includes an S-FPL53 ED glass element"? All these additions can only serve to increase the price. The fact that this item does not seem to be intended purely as a finder is to some extent borne out by the reviews, which refer to its use as a astrophotography camera in its own right. Irony of ironies, one review even mentions the need for a finder to be mounted on it! Which brings me to the next disadvantage of both the Evoguide setup and adapter rings - limited field-of-view.

The FirstLightOptics page for just the guider has an "applet" for determining the FoV of various setups, which shows that the Evo plus ZWO camera bundle can span from M32 to M110 - barely 1 degree. This again would tend to confirm that it is not really suitable purely as a finder for a moderate OTA. Adapter rings tend to have the same problem: Roger's setup can achieve an FoV of over 6 degrees, which is much more usable for star hopping. Finally, although Robin's setup is much nearer to Roger's, he himself says that the webcam he used is not sufficiently sensitive, thus emphasising the need for careful selection of components.

In summary then, although there are products out there which address the same "operational space", there does not seem to be anything currently on the market which combines high sensitivity, very wide fov, and modest cost - unless someone knows differently, that is!

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Yes, Astrosteve: a cheap

Yes, Astrosteve: a cheap finder (likely already have, but with removable eyepiece), the adapter that Tim linked to, and a cheap detector (could be webcam or a low cost CCD/CMOS detector, depending on how much sensitivity, field of view and cost one is happy with). So, all commercially available individually or as the complete unit. Plenty of options for you.

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Finderscope webcam

Yes, the "assemble available components" route is the one Roger hoped he could go down. As I suspect Robin also found though, given his use of Meccano & Jubilee clips, the solution to the problem turned out not to be that simple, particularly in the case of obtaining a wide FoV. He thus had to engage in some creative engineering metalwork (and a crash course in silver soldering!) in order to make everything (literally!) come together.

Given the lack of immediate responses saying "oh yes, I got one of those ages ago", it would seem there is indeed no commercially available unit of this specification available, which answers the first part of Roger's query which I posed in my original post. As to the second part, while he is sure that such a unit would be of great benefit to the beginner, the fact that constructing one is not straightforward leads him to suspect that, now he has (he believes) come up with a workable solution, it is only really a commercial manufacturing process which would be able to build them to a reasonable standard in reasonable numbers. Hence his appeal to members who might have contacts with such an enterprise (or possibly a hot line to BBC's "Dragons' Den"!). Anyone able to help?

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Dragon's Den? "I'm out"

Dragon's Den? "I'm out"

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My digital finder

A few years ago I got the equivalent 50mm guide scope and camera, currently selling for £235 on this page. I think it was more expensive when I bought it and prices have come down. They do various options, including the telescope guider body with a non-rotating helical focuser on which you could put your own camera of choice for £109.

https://www.altairastro.com/guide-scopes-97-c.asp

Of course the main purpose of this setup is as a guide camera rather than a digital finder, but I found it worked perfectly for my purpose. A GoTo mount that wasn't quite good enough to always put the target in the small field of view of the guide camera on a spectrograph.

Best wishes,

Andy

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Starsense and Starlock

There are also the Celestron Starsense and Meade Starlock. The drawback is that I think these only work with their products, but sound a lot like what you describe.

https://www.celestron.com/pages/starsense-technology

https://www.meade.com/starlock/

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Finderscope webcam

Thanks for your input Andy. The item you mention is pretty close to Roger's idea but in fact the "Altair MG32 Mini Guide Polar Alignment Scope + QRB Rings + GPCAM Guide Camera" (phew!) seems to be a closer match - no (un-necessary) focuser and a sensible size objective lens. However, the cameras on both of these are only mono (presumably a colour one would cost rather more) and there's no mention of FoV - but as they are specified to be mainly for guiding purposes one must assume that this could be quite narrow. And then there's the price of course (£275 for the Altair!) when a basic, beginner level, optical finder can be bought for £35 (Rother Valley). Note that I'm not suggesting that the build quality of these two would be anything close to the same, simply that there doesn't seem to be anything available for a beginner.

The Celestron and Meade devices do indeed seem to work only with their own products - and pretty beefy ones at that, judging by the Meade pictures! I suspect that in these cases if one has to ask the price then one can't afford it!

Sorry about the apparent emphasis on price, but this is a factor which should not be overlooked if beginners are to be encouraged to move onto slightly more complicated observations than simply looking at the larger planets. Finding Uranus, Neptune and the brighter galaxies (for example) with only an optical finder on a standard "consumer" 150mm reflector, for example, can be very difficult - particularly for someone with little experience. Adding an "electronic finder", a bit of technology and a star-hopping plan makes things so much easier! Not everyone has large aperture OTAs on motorised, permanently mounted, perfectly adjusted GOTO drives, I'm afraid.

All offers to manufacture gratefully received!

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Refractor?

Silly question, but why stay with a small refractor when a Meade 85mm reflector (or similar) could be used instead?

I've tried CCDs on cheap small aperture refractors and the star images are distinctly blobby because the different colours come to different focuses. 

I've used a reflector as my autoguider/finder for years - run by my own code - and found using a small reflector, with its less blobby stars, more sensitive than when I used the refractor(s).

Would also say, avoid colour cameras as far as possible, the Bayer matrix reduces sensitivity a lot. 

Intrigued by "Star hopping plan". I just used a copy of Uranometria...

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Missing something

I've just realised I missed something in this.

Why not put the camera straight on to the main telescope, display the image it generates, platesolve via a cygwin installation of Astrometry.net and have the software tell you how far to move in RA and Dec to get to the right place. Most Astrometry.net solutions only take 10secs on my 5 year old laptop, so you could point at the rough location and be there 2-3 minutes later.

If you are not autoguiding why have the finder guidescope at all? Eyeballing along the tube would give a good start point. 

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Finderscope Webcam

A really great bit of lateral thinking there Grant, but I feel it doesn't really move us forward. I'm sure that an 85mm reflector would indeed give a better image than a small refractor finder but the practical difficulties of mounting, and probably counter-weighting, such an item on the OTA of the sort of slightly up-market but still essentially "consumer" reflector a keen beginner is likely to be using (something like a Skywatcher 150?) hardly bear thinking about. Then of course, as the 85mm will almost certainly have been intended to be used as a "proper" (if small!) telescope rather than a finder, there is the question of FoV to consider. One might even have to mount a finder on it!! (and round we go again). As for "blobby coloured images", I can assure you that those produced by Roger's device are nicely round and white, right to the edge of the field. [P.S. I sincerely hope you didn't mean "85mm refractor", by the way - available, but not exactly at the budget end of the market!]

We did consider using Uranometria as a guide to star hopping, but I'm afraid the Bodleian didn't seem keen to lend out their copy ....

Moving on to your second post Grant, I knew that Roger had mentioned "plate solving" so I checked back with him and he confirmed that, to put it succinctly, "been there, done that, didn't get the T-shirt". There were two basic problems. Firstly, astrometry.net rarely came up with a solution, even "after the event" let alone "live", probably due to having captured an insufficient number of stars. Then, even if it had found a solution, the instruction to move X in RA and Y in Dec. does rather assume that these axes are correctly aligned and that the relevant setting circles are accurately calibrated and with a fine enough resolution and lack of back-lash to permit an accurate move. With a beginner's telescope which has to be heaved outside and set up each time an observation is attempted, neither of these constraints is likely to be true. If they were, one could of course simply use the setting circles to point directly at the target of interest without having to go through the star-hopping process. As mentioned earlier, not such a problem with permanent installations but a frequent problem with beginners' set-ups.

In Roger's case, the reason he was needing to visually identify exactly where he had got to in the sky after each "slew" between target stars was precisely because he was aware that, although he had taken care to ensure that his equatorial was set up as accurately as possible and that he had turned the dials as precisely as he could, he was aware that the setup was usually just slightly "out" which meant that the end-point was often not quite where it was intended to be. This error could easily be corrected if only he could see sufficient stars to get a "fix" - not possible due to the small FoV of the main instrument and not possible through the optical finder due to low sensitivity. Hence the need for a wide FoV, high sensitivity, "electronic" finder.

And yes, "eyeballing" will certainly give a good starting point but what then? Looking along the tube will give an approximate aiming point but, assuming the target is invisible both to the naked eye and to the (optical) finder, this could be some distance away from the intended aiming point. Even if it's fairly close, unless you know exactly where the telescope is pointing there is no way to know in which direction to move, let alone how far. As above, relying on the RA & Dec. circles may not be helpful, and "random search" (taking images each time through the main instrument) is unlikely to be effective for faint objects.

I suppose a summary of many of the points I have made in all the posts is "Welcome to the world of the beginner"! Everyone has to start somewhere, and that somewhere can be well down the scale of instrument sophistication. Beginners often have problems which "professional amateurs" don't even think of, which can lead to blindness as to reasonable ways to solve those problems.

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Charts

We did consider using Uranometria as a guide to star hopping, but I'm afraid the Bodleian didn't seem keen to lend out their copy ....

How faint do you need to go? Freely available charts reach mag 7.  Here is one of Orion, for example, and another around the NCP.

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Finderscope Webcam

Sorry Xilman - my comment about using Uranometria was just a joke! (replying to the mention of same by Grant Privett in his earlier post). Thanks for offering the info. on star charts though.

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Star hopping down the years

I think you will find that the people on here were all beginners once and most did star hopping and remember it well. Some still go that way by choice. I myself didn't use a GOTO in anger until about 2008 - 37 years since I first had a telescope. While I wanted an LX200 from their introduction onward, mortgages got in the way... An EQ6 eventually proved affordable and is still what I lug outside at night.

My experience suggests that Astrometry.net will generally solve any image with more than 10 stars on with an SNR > 5. I've seen lots of frames solve with 8 stars - but it may take longer. So, what size webcam sensor are you thinking of then? In a 1sec exposure with a 100mm aperture (£60 from a car boot sale) with an uncooled Lodestar I would expect to image stars down to 12-13th mag which with the 100mm gave an ~30 arc minute field. So what field of view are we thinking for the webcam? Could you post one of his pictures?

Also, the idea of using the main scope was mainly for simplification ie no need for finder scope and the camera used could be used for object imaging.

If you had an alt-az mount set up roughly level or a German equatorial aligned by eye to the pole star, by recursively taking images and adjusting the scope slow motions (as indicated by software) either in alt/azimuth or RA/Dec - you would move toward the correct position even if the scope was not properly aligned. The better aligned the quicker it would succeed, but it would still work in a few iterations (unless your alignments were hugely out - a spirit level for alt/az and the pole star would avoid that).

The lack of blobbiness might be explained by the colour webcam having an integral IR blocker (quite common) but the cost of that is lower camera sensitivity and fewer stars.

Re: eyeballing. You don't need to know where the telescope is pointing. If you plate solve, the software will know where its pointing from the plate solution for the middle pixel of the image. Thus it can tell you in which direction to move the slow motions. You just need to move in roughly the right direction.

From where I'm standing - beyond using a guide camera instead of a normal Zoom/Skype webcam - the issue isn't so much the equipment as the software to use it. Its fairly simple though.

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Star hopping

Thanks for your further contribution Grant, and apologies for not responding sooner. I had to communicate with Roger again to find some of the information you requested, and unfortunately he has not been feeling well today so things have been delayed. I'll get back to you as soon as I can.

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star hopping phone app

Just come across this on "Cloudy Nights".  I've not tried it but it looks like you strap the phone to your scope, centre a nearby bright star in the main scope and then use the phone as a "virtual sky" to hop to your target 

https://www.cloudynights.com/topic/761416-need-help-with-validation-of-a...

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Phone app.

Certainly an interesting take on the theme, but it seems to require one to have a smartphone of some sort (which not everyone has, you might be surprised to hear!) but maybe a tablet would work as well? Also, there would appear to be some problems with it yet so maybe not something to take up immediately.

It is, however, encouraging to hear someone else saying that beginners often have problems with star-hopping! Not sure this is the solution, but at least the problem is recognised. Not so sure about the excursion into "plate solving" in the later posts though, as this again fails to recognise that, as the original poster says, the fundamental problem here is obtaining good enough images with basic hardware for plate solving to find a solution - exactly the issue Roger was trying to address.

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Excursion

Still looking forward to seeing one of the images. 

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Finderscope Webcam

And so you shall Grant! But firstly, herewith some responses and information from Roger on the comments in your previous post.

I will of course accept your statement that an "uncooled Lodestar" will get down to mag. 12/13. However .... you didn't say which Lodestar you had in mind but the cheapest device with "Lodestar" in its title which Google could find me was a second-hand Starlight Xpress Lodestar Usb2 Mono St4 Guide Camera (catchy title!) on eBay for £245. Next best was £469 and then it got silly. As mentioned in connection with the similar suggestions from Jeremy, Tim & Andy, even £245 is probably a good percentage of what a beginner might have paid for their entire set-up so a device of this sort is not going to be high on their "must buy" list. The same is true for tripods of course. An EQ6 is no doubt a fine piece of kit, but with a price running potentially into 4 figures it's not really a budget offering! When one is working with more basic, less highly specified, equipment and a desire to be more frugal, different solutions are needed.

So, to cut to the chase, of what does Roger's finder consist? Camera first. It's actually a ZWO ASI 034MC webcam, "bought used on eBay some years ago for £30" and obsolete now, of course. This is mounted at the eyepiece end of a basic 6x30 optical finder by use of an array of metalwork and adapters, including an internal focus tube using a webcam lens bought from China to allow the ZWO to image afocally. Total cost? Less than £50. Clearly neither practical nor desirable to make an exact copy were it to be manufactured, but Roger estimates that a "proper" version could be made for £100 all in and ready to mount & use.

Now performance. Its field of view is in excess of 6 degrees and stars down to at least mag. 8 can be clearly imaged with even field illumination and very little distortion. Just right for visual identification of direction of view when star-hopping in fact, obviating the need for potentially troublesome plate solving and therefore for an accurately adjusted and calibrated tripod.

And finally a picture. Please bear in mid that this is a test image taken when the device was undergoing development, so it is neither quite centred nor in the correct orientation (needs rotation by 105 degrees anti-clockwise for "sky equivalence"). Roger hasn't needed to take any such images when using the finalised version for actual observations, as it works so well, so I can't post any. But this one is an unprocessed single frame, exactly as taken - just reduced in size for ease of posting.

This image has been chosen to show that the FoV is indeed around 6 degrees - the brightest stars are Merak (left) and Dubhe (right) which are separated by 5 deg 22.43 min. It can be seen that the star images are circular right to the edge of the frame and free of false colour, and there is uniform field brightness.

A pretty useful piece of kit, I would say, and at a potentially very attractive price. Any budding entrepreneur care to change their mind as to manufacturing possibilities before it's snapped up by the PRC?

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Camera

I think I would be a bit worried by that image. Those are first and second magnitude stars! What sort of exposure are you using there? The camera allegedly has a 60% QE and is only 8 bit, but is good for exposures up to 60s apparently. I'm kind of hoping that's a 1/25th sec exposure, as I would really expect to see more than that.

On plate solving. Its the elegant way to solve the problem. A stick on spirit level is hardly a demanding set up and you don't need to buy a finder as you just use the main scope and also don't need to consult charts - so its a cheaper solution too.

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Finderscope Webcam

Sorry Grant but you do seem to be persistently mis-understanding (or mis-construing) many of the points being made here. As I clearly said in the text of my post, the image I attached was chosen mainly to prove that the "electronic finderscope" did indeed have a uniform, undistorted, FoV of around 6 degrees - twelve times greater than that of the set-up you mention and therefore of much geater use as a finder - not to illustrate that it could capture 2nd magnitude stars. In fact, by looking only a little more carefully at the image (helped perhaps by an expansion of the page in the browser), one can clearly make out very much fainter stars - down to at least 8th magnitude in fact, as claimed in the post. I admit that the need to reduce the image for convenient display in the post has made this slightly less convenient so here's a larger view of just the bottom-left corner which has been enhanced so as to make things even easier.

As you will be able to confirm, the star visible towards the edge of the frame 45deg down and left of Merak is magnitude 8.38, that to Merak's right (just below the cross-hair) is mag. 7.94, and there are several more stars visible of somewhat greater brightness. This number of stars of that range of magnitudes in a FoV of this size makes it very easy for an almost real-time assessment of the direction of view to be made by comparison with whatever star chart or program one is using to carry out the hopping process. This ease of  "manual plate solving", if you will, makes consulting astrometry.net entirely un-necessary.

And don't forget that this is just the image through the finder. Once the target (or the field in which the target is known to sit, for very faint objects) has been located and centred in the wide FoV of the finder, attention can turn to the greater light-gathering power and magnification (but also very narrow FoV) of the main instrument in order to make observations. This is far simpler and much faster than carrying out both the alignment and observation operations through the main instrument, especially for a beginner for whom, as I must seemingly keep on reminding everyone, this device is intended.

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A 6 x 30 finder is pretty

A 6 x 30 finder is pretty small, Astrosteve, so perhaps not surprising he was having trouble finding targets. I'd recommend a 50 mm finder as this should allow a beginner plenty of opportunities to star hop without resorting to electronic gadgets. You can pickup finders of really good quality quite cheaply these days. They have a field of ~6 degs and should easily get to mag 9.5.

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Finderscope Webcam

A very good point Jeremy, which I put to Roger to ask for his comments. He said that when he discovered the problem with the 6x30 finder (which was simply the one supplied with his telescope rather than a deliberate purchase) he did indeed consider getting a 9x50 but, as he already had the old webcam and other "bits & pieces" from earlier projects, he decided to give the "electronic" option a go first. It was really only when he discovered that the prototype device worked so well, and that it might be able to be manufactured for a price comparable to that of a 9x50, that he began to think about whether it could be commercially produced.

While the webcam finderscope and a 9x50 will have about the same sort of performance (in terms of FoV and sensitivity), the electronic option does have a number of significant advantages over its optical cousin, which I noted in my very first post:-

1) The view seen through an electronic finder can be easily manipulated, both mechanically and by use of the driver program, to align it with that given by whatever star map or program one is using to define the hopping sequence. This includes the ability to "flip" the image in two axes as well as rotate it, something which is impossible to achieve optically without the use of additional lenses or prisms. It should be noted that, as Roger pointed out, the image in an optical finder is inherently "upside down" but the orientation changes if, for example, a diagonal prism is in use, all of which can be confusing for a beginner. The ability to easily alter the image orientation avoids these sorts of issues.

2) An electronic finder provides the observer with a much more convenient "operating environment". Even a diagonal prism cannot always avoid the need for a most un-natural stance to be adopted in order to look through the eyepiece of a finder. Viewing the scene on a screen removes this problem.

3) Use of a camera enables the observer to take images during the hopping sequence, which can be useful for analysis after the event (particularly if the sequence went astray somewhere) and to document the sequence, perhaps to teach someone else how to carry out the same operation.

4) Driver software could enable the viewed image to be processed "on the fly" in order to improve the image quality and hence the effective sensitivity, which might permit objects at the limit of detectability to be seen.

Roger also noted that he had tried a 9x50 and found that although the performance was indeed a little better than a 6x30 it was not significantly so. While less bright stars could be seen, the difference was small and the FoV was 1 or 2 deg. less than achieved by his device. In addition, the 9x50 was much heavier which required extra weight to be added to the OTA counter-weight in order to maintain its balance.

All the above persuaded Roger that the device he has created would be of considerable benefit to a less-experienced observer, hence his request that I begin this post.

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4.2 from the East German judge

I obviously misunderstood your intent. I thought cost and convenience to the user was everything. Several members, in response to your request, suggested a variety of approaches that you felt failed on cost grounds. I suggested an alternative approach that required only the purchase of a simple camera, a stick on bubble level and a bit more effort with the software driving the camera. No engineering required. That seemed the cheapest and simplest option for supporting the cash strapped beginner.

Also, I must apologise, I had not realised that when you grabbed a chunk of the image frame you resized it using a method that so badly affected the apparent performance. The dimmer stars are pretty poorly shown. You might want to use a bicubic spline or similar next time. See attached.

Yes, the image section you now supply is much nicer and, as it happens, the image solved with astrometry.net, so you could obviate the need for charts.

I look forward to seeing Roger‘s design hit the market place, but think the commercial mark up will probably take it above the cost of a new ZWO 120mm or the systems sold by Altair, unless made in bulk.

But we're into vanishing returns here...

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Thread closed

This sub-thread of the "Finderscope Webcam" topic is now closed to further comments.

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not a webcam

The ASI 034MC was an astro camera not a webcam though and cost new similar to the current equivalent ASI120  (~£120). Cheaper domestic webcams would not go as deep. Add to that the cost of the specially adapted guidescope and you can see why a commercial equivalent to this design is going to cost ~£200

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Finderscope Webcam

Ah, yes, quite right! It's a big "mea culpa" from this end, I'm afraid. Apologies for this "terminological inexactitude" but when one has recently spent some time reviewing and assessing webcams for Skype & Zoom compatibility and usability as outdoor observation devices the term does eventually attain a sort of generic applicability!

However, whatever one calls them, I feel that the retail cost of a complete astrocamera unit (whether in the past with the 034 or currently with the 120) is perhaps peripheral to the issue in hand. As you yourself imply, it would clearly be uneconomic for a manufacturer wishing to duplicate Roger's device to buy a complete unit and install it in a housing of his construction. Given the presumed ready availability of "bare" sensor modules nowadays (led by the revolution in the quality of smartphone imaging systems), a manufacturer would clearly only have to buy a module, not all the associated mounting and focus gubbins, at a wholesale price very much less than that of a complete unit. Hence Roger's assumption that an all-in price of £100 or less is entirely feasible, given also the simplified nature of the mounting housing.

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Beginners speak well of this

Beginners speak well of this kind of finder scope, which is quite reasonably priced compared to a digital device: https://www.firstlightoptics.com/finders/astro-essentials-9x50-right-angled-erecting-finderscope.html

It gives a correct image so the orientation is the same as seen by the eye. It has a right angled eyepiece so might be a bit more accessible to view. Astrosteve mentioned that both characteristics are important to Roger, who will also be able to ditch the power supply, computer/monitor, cables, software and other paraphernalia that beginners might struggle with.

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Finderscope Webcam

Thanks for the new information Jeremy, and the link to the Astro Essentials finder. I had in fact come across this device when I did a search for 9x50 finders after your last post but was unsure of the quality of such a device at this price point. It's thus reassuring to hear that "beginners speak well of this kind of finder scope".

On the downside however, one reviewer does mention the "weight" issue which Roger encountered with the 9x50 he tried. And while the erecting prism will give a corrected view, this is only true for one orientation of the optics. If the prism is removed or rotated (for "observational convenience"), the view will change in a way which might be confusing to a beginner (as I previously noted). Also, an optical device lacks the other advantages of an electronic device which I mentioned in a previous post.

In the end though, it will probably come down to a price/performance trade-off - even at this level of cost. A beginner just starting out or one not wishing to become involved with the "paraphernalia" you mention would undoubtedly find the Astro Essentials device a good fit for their needs. It is unlikely that a device such as Roger has built could be commercially constructed for a similar price to this optical finder, but a beginner wishing to take the next step in imaging might well be prepared to pay a little more for the extra advantages an electronic finder confers while still keeping things well below the price of the sort of finder/guiders mentioned at the beginning of this topic. In other words, there might well be a gap in the market which Roger's device could fill.

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Plate solving.

Now wondering how much extra it would cost to go the whole hog and put a plate solver into the system. A Pi with a 32G SSD would have easily enough power to run it. Use a phone as a display and controller over wifi. Optics are 50mm refractor and web cam on a standard finder bracket, to which the Pi would also be attached. A pity a USB cable would still be needed but a rechargeable battery could presumably be attached to the mount somewhere, even on a Dob.

Major development cost would be writing software.

Hmm. I have a Pi-3 over in La Palma. Might have a play when I return there.

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Platesolve

The code for plate solving under Python is pretty trivial. I've got a copy if you ever want it.  

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Re: Platesolve.

Thanks, but I already have it myself. Anyway, the Pi has a fully functional C compiler and Perl interpreter which are my languages of choice and how I implement such code on all my other Linux boxen..

On further thought, I also have the Pi IR-enabled camera so no need for a web cam, USB connection, fancy interfacing software, etc.

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Perl

Have fun with that. I never got over versions 4.99, 5.00 and 5.001 all giving different answers to one script I used. :)

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Perl

I've not used Perl anywhere near that ancient in a very long time and have never had significant problems in the last 20 years, despite having written at least 20k lines of Perl over that time.  You got caught up in the Perl 4 / Perl 5 changeover, which was at least as big as the Python 2.x - 3.x transition. People, including myself, are still suffering from that one 18 months after 2.x EOL and several years after the writing appeared on the wall.

Although religious arguments are great fun I suggest that we should take this one elsewhere and return the thread to matters astronomical.

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Perl

Not sure why I ended up with 2 copies of the Perl comment. But to clarify, it was in about 1996 when I was maintaining some astronomy code for a PPARC project called.... Starlink. Code that is still available for Linux.

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Finderscope Webcam

Although Roger is unable to update the postings on this topic himself, he has been keeping a keen eye on the lively discussions in "read only mode", as it were, and advising me on possible responses. However, now that things seem to have quietened down he has suggested that the topic be brought to an end.

Accordingly, he has asked me to forward his thanks to all those who took the time to suggest possible hardware solutions which embody similar functionality to his prototype device even if, in several cases, they sit at a much higher price point or, in the case of the 9x50 finder purely optical solution proposed by Jeremy, lack a number of distinctive features which can only be provided "electronically". He remarked that he is actually encouraged by the fact that no-one has come up with an electro-optical device which has all the functionality required by a "beginner improver", and no more (no need for focusers, replaceable eyepieces, filters, multi-element optics etc.), which might perhaps indicate that there is a gap in the market for a device such as his if it can be manufactured at a reasonable price. Proving it might be more of a problem though!

In closing, we both wish everyone "Clear Skies" and good observing.