Scope recommendations for Galaxies & smaller DSO's

[teoria_del_big_bang]

Currently all of my limited imaging is done with my Esprit 100ED + QHY268M. And for many DSO's it works well but when it comes to galaxy season for me it is a bit of a waste of time due to the FOV. Also it does not yield great results for smaller DSO's like dumbell and bubble etc.

I did buy a RC6 to hopefully get a better FOV for these objects but after a year I am still struggling to collimate it properly and am maybe thinking I could do better with a different scope.
So any recommendations ?
Ideally I could do with something not too expensive, easy to collimate if a reflector, something that my CEM60 mount will handle with ease and I would want to use it with the QHY268M or possibly the 1600M. 

Steve

[DaveS]

At one time I would have said big RC or similar, 12" aperture / 2m+ FL ...

BUT

As @ollypenrice has repeatedly said, with today's sensitive small pixel CMOS cameras (Like your QHY268M), then maybe a 130 -150 mm 'frac of 1 metre FL . There are too many options for me to single out one particular model, and in any case it will depend on your budget, and the load carrying capacity of the CEM60 mount.

[teoria_del_big_bang]

6 minutes ago, DaveS said:

At one time I would have said big RC or similar, 12" aperture / 2m+ FL ...

BUT

As @ollypenrice has repeatedly said, with today's sensitive small pixel CMOS cameras (Like your QHY268M), then maybe a 130 -150 mm 'frac of 1 metre FL . There are too many options for me to single out one particular model, and in any case it will depend on your budget, and the load carrying capacity of the CEM60 mount.

I understand there are a lot of choices (if you can find stock anywhere 🙂 ) hence my indecision.

Budget I would say under £1k but could stretch a bit if necessary.
Payload, according to specs is 27Kg, but unlike some mounts it does not state different payloads for visual and AP just the one 27 Kg.

I was erring towards a 150 frac but just wondered if I would still end up over-cropping the images.

Steve

[DaveS]

At under £1k, then I think a reflector will be the only option, as even budget 130-150mm apo 'fracs are going to be three or four times that, and don't even think Tak, or TEC .

FLO have the 8" Stella Lyra RC in stock at under your budget.

Have fun with the collimation.

[vlaiv]

27 minutes ago, teoria_del_big_bang said:

I was erring towards a 150 frac but just wondered if I would still end up over-cropping the images.

I guess it depends how you look at it.

Maybe instead of starting at FOV / Focal length / Sensor size - you start by what you think can be achieved in terms of resolution in arc second per pixel.

If you say - I'm able to achieve 1.4"/px images with 8" scope, then let's see what sort of pixel size (including binning) will I need on EdgeHD (which I believe is less trouble to collimate than RC). Maybe it will be MN190 instead?

Anyway - you start with 1.4"/px - then you say, ah, but most galaxies are in fact less then 10' in extent, and that is only 600" in extent, so I'm looking at 600" / 1.4 = ~430px for a galaxy at best.

That will be rather tiny on 3000x2000 px sensor, so all I really need is maybe 1600x1200px to capture galaxy and surroundings.

With ASI1600 - that allows me to bin say x3, so my effective pixel size will not be 3.8um but rather 11.4um and I'd need ~1600mm of FL to get there (at ~1.4"/px).

So there you go - don't expect very big galaxy images, as galaxies are small. Use "slow" scopes as it is easier to work with them. Compact design has advantage as far as mount goes, so SCTs, RCs and such. Get as much aperture as possible, as it impacts achievable resolution as well as helps with light collection.

[DaveS]

You might also add a Telecompressor if 1600 mm is too long. I *think* it will cover APS-C.

[DaveS]

Ah, I had forgotten the 190MN, the "poor man's 7" apo". Could be a good choice.

[ollypenrice]

21 minutes ago, DaveS said:

Ah, I had forgotten the 190MN, the "poor man's 7" apo". Could be a good choice.

It's very strange that this instrument has 'gone quiet' and also strange that nobody makes bits to enhance it mechanically, since it has always struck me as offering great optics.

Olly

[teoria_del_big_bang]

On reflection I probably was a bit quick to say sub £1K , I sort of stated this thinking in the end I would spend more anyway but to tell myself that was the original budget.
I probably would have to spend nearer the £2K and all along was very impressed with the Edge 8". 

Steve

[wimvb]

8 hours ago, vlaiv said:

Maybe it will be MN190 instead?

 

8 hours ago, DaveS said:

Ah, I had forgotten the 190MN, the "poor man's 7" apo". Could be a good choice.

 

7 hours ago, ollypenrice said:

It's very strange that this instrument has 'gone quiet' and also strange that nobody makes bits to enhance it mechanically, since it has always struck me as offering great optics.

Olly

The 190MN is a very nice scope, and if I had the place and money, I would love to get a "second serving" (on its own mount). But the OP mentions easy to collimate. With a few years experience, I can vouch that this scope is not straightforward to collimate at all. But if you get it aligned properly it's a gem.

@ollypenrice, I'm about to remedy the mechanics part. In August I ordered a 2" FeatherTouch focuser for my scope. The original is just too unreliable with its built in extension tube. Unfortunately FeatherTouch focusers have a long lead time. Astroshop informed me a month ago that I shouldn't expect delivery before new year.

[teoria_del_big_bang]

Well after looking about a bit more it looks like the best option is a Celestron Edge 8".
I know there is still collimation but it looks to be easier than the RC and from reports stays in collimation well.

So the next thing to look at is what else do I need. There is a dedicated 0.7 reducer but the blurb seems to say that for flatfield this is not required so is this just a genuine reducer and not a flattener / reducer ? Should I go with this reducer from the start rather than finding I am better off with it and then introducing it to the image train ?

Also, fitting a motorised focusser does not seem to be too straightforward and many seem to think the Moonlight is the only way to go (or a FT).

Anyone on SGL able to help me with their setups of this scope ?

Steve
 

[scotty38]

46 minutes ago, teoria_del_big_bang said:

Well after looking about a bit more it looks like the best option is a Celestron Edge 8".
I know there is still collimation but it looks to be easier than the RC and from reports stays in collimation well.

So the next thing to look at is what else do I need. There is a dedicated 0.7 reducer but the blurb seems to say that for flatfield this is not required so is this just a genuine reducer and not a flattener / reducer ? Should I go with this reducer from the start rather than finding I am better off with it and then introducing it to the image train ?

Also, fitting a motorised focusser does not seem to be too straightforward and many seem to think the Moonlight is the only way to go (or a FT).

Anyone on SGL able to help me with their setups of this scope ?

Steve
 

Is your plan to lock the mirror and put a "proper" focuser on it then?

[teoria_del_big_bang]

2 minutes ago, scotty38 said:

Is your plan to lock the mirror and put a "proper" focuser on it then?

Looking at what others had done for AP yes I thought that was the best option, unless there is a better way.

Steve

[scotty38]

11 minutes ago, teoria_del_big_bang said:

Looking at what others had done for AP yes I thought that was the best option, unless there is a better way.

Steve

Yes from what I've read I'd agree too. I was checking you were taking that route versus replacing the stock device. Interested how this pans out.....

[teoria_del_big_bang]

2 hours ago, scotty38 said:

Yes from what I've read I'd agree too. I was checking you were taking that route versus replacing the stock device. Interested how this pans out.....

Well that's the current thoughts, but probably will not happen as quick as I would like - need to acquire the funds first thing and then see what stock is available (I think the scope if I go 8" is not an issue although tempted by the 9.25" but not sure what I really gain between the two scopes, except a lot more weight to guide and it is another £1K more so maybe stick with the 8").

Also it seems most seem to go with the OAG and not a piggy-backed guidescope which is all new to me.

Steve

Edited October 15, 2022 by teoria_del_big_bang

[wimvb]

32 minutes ago, teoria_del_big_bang said:

Also it seems most seem to go with the OAG and not a piggy-backed guidescope which is all new to me.

Not really an issue. Once the oag is installed and is focused (I use a Bahtinov mask and a zwo helical focuser), it just sits there.

[Elp]

The oag is more so because of the focal length of the scope, even with the f6.3 reducer you'll be hard pressed finding a light guidescope (going to be more like an actual telescope) to match the imaging focal length/resolution.

[teoria_del_big_bang]

30 minutes ago, wimvb said:

Not really an issue. Once the oag is installed and is focused (I use a Bahtinov mask and a zwo helical focuser), it just sits there.

Thanks for that, it is just something else to fit in the train behind the reducer so I might have to leave my rotator out, although probably not an issue as most targets will fit in the FOV without having to rotate to fit it in.

4 minutes ago, Elp said:

The oag is more so because of the focal length of the scope, even with the f6.3 reducer you'll be hard pressed finding a light guidescope (going to be more like an actual telescope) to match the imaging focal length/resolution.

Yes that makes perfect sense to me now why it is necessary.

Steve