Cosmic Geoff

1 hour ago, Martin Meredith said:

Is your 8" f/10 scope reduced or operating at its native focal length (and if so, are you guiding?). If native, you might also have issues with the small FOV (0.14 x 0.1 degree) for that combination in terms of getting enough stars to stack (or platesolve, if you do that). Under the right circumstances (great tracking and seeing) there are PNs that ought to turn out well with that setup, but much of time I imagine it will be a struggle.

Noted. I am thinking that I may buy a 0.63 focal reducer.

I have read this thread with interest as I have been imaging a number of the same PNs and recently have tried re-imaging a number of PNs recorded with 102mm f5 achro and ASI224MC camera, this time using a CPC800 (8" f10 SCT) and ASI224MC.

Examples of NGC 2392 are attached. These are single images (for other objects I achieved live stacked images) The more populated image is taken with the 102mm.  The images taken with the 8" SCT generally show more detail of these very small objects but the exposures are much longer.  The results seem limited in exposure by the Bortle 6 sky-glow and in resolution by the bad seeing.  For instance I have not been able to image NGC246 (pictured in this thread) at all.

I have not decided what combination of telescope and sensor works best or what upgrade of equipment might be worth considering.

I should think that unless Celestron can supply the missing part, your other options are to find a scrap 4SE (unlikely) use a diagonal on the camera port, or to have a new eyepiece barrel made by a machine shop.  The last would be easier done if you still have the lower, threaded portion and can purchase a 1.25" extender to rework.

I bought a Startravel 102mm initially on impulse, to complement my 127m Maksutov.  I found little use for it (yes it does widefield but in Bortle 6 skies this is rather underwhelming) until I found it worked well as a budget imaging scope for EVAA (q.v).

The 127mm Maksutov is an instrument with various uses, and is one you are likely to want to keep.  The Startravel is likely to be less versatile.  I have telescopes similar to both, and rarely use the Startravel for anything other than basic (EVAA) imaging of deep sky objects. The obvious visual application of a Startravel is for widefield views, but in practice in Bortle 6 skies the results are under-whelming.

If you can afford (or want) GoTo it greatly extends the things you can do with a given telescope.

I have a Starguider budget binoviewer, and found it can be tricky to use.  It adds about 100 mm to the optical path, requiring a major re-focusing.  The distance between eyepieces has to be adjusted to suit your eye spacing. Mine came with a pair of short-barrel 30mm Plossl eyepieces (no undercuts) and it worked much better with these than with my alternative - a pair of 20 plossls, one with undercut. With the latter it was very difficult to merge the images, With the two included Barlows, sharpness was poor except in the middle of the POV.

When everything works right, e.g. on the Moon, the views are amazing.

I have one of these and I carry it securely by gripping either the main tube or the dovetail bar.

I really don't see the point of fitting a handle.

You can definitely take planetary images with this Maksutov + a dedicated planetary video camera.  You do not need an equatorial mount for this and you could use the AZ-GTI mount, but a more rigid mount and tripod would make the excercise less trying.

And you do not need a Barlow lens with this scope.  Also a scope with this focal ratio is relatively forgiving of eyepieces, so you can select Plossl eyepieces for the lower powers if your budget is limited.

I have the Astro Essentials 50mm finder/guidescope, which comes with a proper focuser, takes 1.25" eyepieces (or T2 cameras), and comes with a two-ring mount on a dovetail bar that fits in a standard Synta finder shoe. (the mount rings alone might cost the asking price elsewhere.) I thought I could make it plate-solve with suitable attachments, but unfortunately it does not do this well under Bortle 6 when pointed at a random sample of sky.

So what else is it good for? Guiding, I suppose.  There does not seem to be enough focal depth to fit any sort of diagonal.  It might do as a high-powered finder for planetary imaging (so long as the planet is not at too high an altitude).

The line of least resistance might to buy a used Windows laptop (pallet-loads of them refurbished from dealers on ebay) and use that for imaging rather than your expensive MacBook. Much more astro software is available for Windows.

You do need an IR cut filter. I tried my ASI224MC in daylight without one and the colours looked off.  I ordered the ZWO IR cut filter with the camera, and also their IR-pass filter (since both filters were quite cheap).

When I was a lad I made an equatorial fork mount for a 8" F7 newtonian.  I used sections of 3" diameter steel pipe screwed together with standard angle and T fittings., with roller bearings for the 'shaft'.  It was not as rigid as I hoped, IIRC.

Another suggestion is to look at the design of the Celestron CPC range of mounts and copy them.  They use an alt-azimuth turntable which can be wedge mounted. You can find out from published materials how the axes are clutched and driven.

I use a ZWO IR cut filter, which cost about £20. It does its job, which is to eliminate the odd colour balance one would get if using an IR- sensitive camera without the filter.

You should be able to find a pair of holes that match with this finder shoe on your SCT.  I can't say whether this will be the RDF mounting position. 

I actually used a different (cheaper) mounting shoe on my C8.  You don't want to start drilling and tapping holes.

The chassis transformer you cite will do. But wouldn't it be less work to use one of the ready-made units? You do NOT have to match the wattage of the original TAL unit. Any 12v transformer capable of outputting 0.8A OR MORE will do just as well.  It will output 0.8 A when connected to your motor, regardless of its capacity.

I have had a look at the PSUs.  The panel mounted one is only 3VA so clearly unsuitable.

You should be able to select a Pulsar unit that is:  UK plug, 12v AC output, and delivers at least 8,5VA e.g. 8.5, 12, 15 or 20VA (and is in stock🙂).  The more powerful ones seem to cost more. You also are expected  to select the style of output plug (2.1 or 2.5 inner)  I realise that neither plug may fit your motor, but...

18 hours ago, Cornelius Varley said:

The Tal2 uses an AC synchronous drive rather than dc stepper motors.

That 'synchronous' makes me wonder if the synchronous motor is self-starting. If it isn't, maybe the power pack is OK and the motor has a kick-starter you have overlooked.  (I have a synchronous mains clock that needs a smart tug on the setting knob to start it running.)

Your PSU has a British label on it which suggests that, as you suggest, it is a replacement.  You need a multi-test meter to check this gear out.  

For a competent person, making up a new PSU should not be hard. It just has to supply the right voltage and an adequate amount of current.

6 minutes ago, Cornelius Varley said:

The Tal2 uses an AC synchronous drive rather than dc stepper motors.

If that's the case, the supply presumably consists of a step-down transformer, and the problem can be solved by finding where there is a bad connection and fixing it, or replacing the faulty transformer with a new one that gives 12v output with a minimum of 8,4 watts.

Writing as a former electronics engineer: it definitely says "12v AC", but why?  One could easily get 12v AC from a transformer, which is not a flat object, wheras a 240v to 12v DC power supply would look more like the object in the photo...

Do the insides of the PSU, or the motor, offer any further clues?

If you happen to own a Startravel 102mm you can have a go at using it for imaging, and you can get some results.  But if you want to do some serious deep-sky imaging you should buy something like an ED scope - the experts can advise which one.

You will also need an expensive heavy-duty GoTo mount and (I suggest) the book "Making Every Photon Count" by Steve Richards, available from FLO.

There are various other choices and some people will recommend a Dobsonian mounted scope (because nearly all your money goes into the telescope rather than its mount).

If you really want one of the two you cite, either would be fine. I have a Startravel 102mm f5, which is a bigger aperture and shorter focal ratio than the Evostar and while I can see the chromatic aberration it's not generally a critical problem.  The Maksutov should be a fine scope (nobody ever complains about having a bad one) and is a size smaller than my Maksutov - an instrument I intend to keep. 

Either would be a handy grab'n go scope regardless of what you buy or upgrade to later.

1 hour ago, Deepblue12 said:

I've actually just found a link how to remove the Corrector plate on the 127 so i'll do that which should then allow me to see the mirror directly. (which hopefully will be clean)

I would suggest that you clean the outside of the corrector plate and see how that goes before you think of removing it.  The corrector plate already has an obstructing mirror stuck in the middle of it, so a few specks of dust on the inner surface or on the main mirror are not going to make the performance any worse.

The picture shows a significant amount of dirt on the outside of the corrector plate. There is no evidence in the photo of any dirt inside.

How do you know that the mirrors (enclosed inside the scope body) are dirty? How would the dirt get in there? Dismantling these scopes is not a task for novices.

If you are not confident about cleaning the outer surface of the corrector, it would be wise to let someone experienced do it.

On 09/01/2022 at 12:52, clafann1 said:

telescope model is: Bresser Solarix 114/500

That is a rather short focal ratio (f4) better suited to low power work eg viewing star clusters etc.  It is likely to be quite demanding of eyepieces so I suggest you buy some decent ones (which can also be re-used with a future scope purchase).