Find me a scope - please

[groberts]

For some years I have been successfully using a WO GT81 with a SW AZEQ6 GT mount and a ASI294MM pro camera for imaging, which has been excellent + I also have a Samyang 135 rig + ASI 1600MM-Cool camera for widefield. Notwithstanding, I find the mount increasingly difficult to move around, especially down the garden, which is the only location I can see the north sky from (my house obscures Polaris etc. from my main astronomy site) and as an alternative have been following the development of the lighter Harmonic drive mounts over the past 18-months with great interest.  Last week I pushed the button on the ZWO AM5 which has just arrived and, I hope, will provide several possibilities but mostly portability (1) to establish regular imaging platform at the end of the garden all those lovely north sky objects I’ve been missing and (2) maybe travel to dark sky sites.             

I'm therefore now thinking about a scope with more reach than the WO GT81 (which I will continue to use) but not too big i.e. more suitable to galaxies etc e.g. longer FL and greater aperture. Whilst not ruling out something like the Celestron Edge range, though first and foremost I'm really a refractor fan and would prefer to go down this route if possible.

Ideally it would be good to run the AM5 without balance weights i.e <=13kg total weight, so I'm thinking light weight is important (maybe carbon fibre?), and perhaps 100mm to 120mm aperture, probably combined with either another ASI 294MM Pro camera or the ASI 2600MM?

I’ve been trawling the internet over the weekend and a few that have got my attention: the new ZWO 107 APO refractor range or ASKAR (103 or 107) equivalent, Starfield 102 ED + SW Esprit 100ED or  Stellamira 90, though these maybe too close to my WO GT81?

Anyhow, I would appreciate any thoughts / recommendations please, particularly those with first-hand experience?

Graham
 

[Elp]

Been there, done it.

Started with a Z61, then went to 130PDS, didn't like the bulk of it (even though it's a small Newtonian and the FL wasn't much different from the Z61), then went to C6 which I still have. Also bought a Starfield 102 as a medium FL between the two. The Starfield is good, but note they start to get much longer and heavier especially if you decide on a triplet. None can match the SCT for raw FL on planets (if you want to do this) and the majority of galaxies are tiny, and also the aperture of the C6 provides better resolution, but the refractors are sharper. It depends what you're aiming for personally.

Carbon fibre tripods are also good (I hated the steel type due to the added weight and the fact they don't compact down short enough, they're sturdy though if you get the right one). With everything set you should have a decent and easily moveable setup, I know when I went HD it was a revelation not having to amble about insecurely with the off balance of CWs (also less setup time as no need to balance Dec/Ra where applicable).

Edited October 30, 2023 by Elp

[vlaiv]

Here are my thoughts on this - mind you, I don't have first hand experience with said mount and scopes of that class on it.

You want a triplet rather than doublet for serious imaging. You want as much aperture you can mount.

This really limits you to below 130mm refractors as scopes in that class fast approach over 10Kg in weight.

Here are two contenders that I managed to quickly track down:

https://www.teleskop-express.de/shop/product_info.php/info/p10181_Explore-Scientific-ED-Apo-127-mm---FCD-100--carbon-tube--Hexafoc.html

127mm triplet with ~7Kg of weight

https://www.teleskop-express.de/shop/product_info.php/info/p3041_TS-Optics-PHOTOLINE-115-mm-f-7-Triplet-Apo---2-5--RAP-focuser.html

This scope comes under many labels, and I'm sure there is AltairAstro version as well that could be much easier to source locally.

115mm triplet with ~6.5Kg of weight

[M40]

Always one to be different, your wo gt81 has a similar fov to my 85mm, so how about rather than a new telescope, how about a new camera in the zwo asi462mm. Have a look in the fov calculator and see what you think 🤔 

[vlaiv]

9 minutes ago, M40 said:

Always one to be different, your wo gt81 has a similar fov to my 85mm, so how about rather than a new telescope, how about a new camera in the zwo asi462mm. Have a look in the fov calculator and see what you think 🤔 

How will that help with "more reach" requested (i.e. longer FL and more aperture)?

[M40]

Just now, vlaiv said:

How will that help with "more reach" requested (i.e. longer FL and more aperture)?

If you compare the wo gt81 and the zwo 294 on for example m51, then swap the 294 for the 462 it's a completely different fov. The camera will always sell on if it doesn’t prove it's worth.

[vlaiv]

Just now, M40 said:

If you compare the wo gt81 and the zwo 294 on for example m51, then swap the 294 for the 462 it's a completely different fov. The camera will always sell on if it doesn’t prove it's worth.

Well, if you want to get different FOV - just crop 294 instead of spending money on 462 to have to sell it later

[DaveS]

Just to think outside the box, how about a Richey-Chretien?

[bosun21]

Another option is the Stellamira 125. It’s a carbon fibre tube so nice and light. It’s a doublet though but has the equivalent of FPL53 glass. If you want a triplet this size then the weight will be considerably more.

[Clarkey]

I have the AA Starwave 115mm refractor which is excellent. It's FPL51, but the colour correction is very good. It also makes an excellent visual scope. I also have an RC8 which is also very good. The RC8 binned has the extra aperture and is 'faster', but in terms of image quality there is very little in it. The RC8 is quicker to cool, but as they are permanently installed in an observatory it is not really an issue for me. For galaxies the RC8 is excellent value for money.

[M40]

27 minutes ago, bosun21 said:

Another option is the Stellamira 125. 

Now thats a nice telescope and the one on my wish list for when I run out of targets with my current setup 👌 

[vlaiv]

4 minutes ago, M40 said:

Now thats a nice telescope and the one on my wish list for when I run out of targets with my current setup 👌 

It would be nice if someone would come along that has actually used that scope for imaging.

I've read reports that it is excellent visually, but faster ED doublets don't control color as good when imaging.

For example, I was surprised to see level of residual chromatic aberration with 4" F/7 ED doublet with FPL-53 glass. I was expecting something like that from cheaper FPL-51 glass ED doublet but not from FPL-53. Now, granted, this scope is slower at F/7.8 - but it also has larger aperture (significantly so).

For comparison - Skywatcher ED100 that is often used for imaging has F/9 and is almost color free. ED80 is not quite there although it is 80mm and F/7.5. And this is 125mm F/7.8. Closest thing to it is SkyWatcher 120mm F/7.5 and I know that some people use it for imaging as well - but I have no idea how well it performs with respect to chromatic aberration.

There is a cure for that - in form of L3 Astronomik luminance filter, but I'd rather use sharp triplet than resort to such hacks on doublet (although I would not mind using doublet + filter if similar triplet was unavailable for some reason or too expensive for me).

[M40]

33 minutes ago, vlaiv said:

There is a cure for that - in form of L3 Astronomik luminance filter, but I'd rather use sharp triplet than resort to such hacks on doublet (although I would not mind using doublet + filter if similar triplet was unavailable for some reason or too expensive for me).

Absolutely, but for me a triplet of that size is out of my pocket and twice the weight putting it out of reach for both me and the mount.

[groberts]

Thank you all for the comments so far - I'm erring towards the ZWO 107 or its Askar equivalent but really wondering how much more I'll get moving up from the WO GT81 I already use.

If anyone has either of these, do you use it with a focal reducer or not?

Also, ASI 294MM Pro or ASI 2600MM Pro?

Graham

 

Edited October 31, 2023 by groberts