Newbie refractor dilemma!!!!

[Nugs]

So i have made my mind up that i need want a smallish refractor (up to 75mm ish) to aid me in my foray into imaging.

Im currently using a Skyguider Pro tracker with my Olympus EM1-ii with various lenses, which i will keep for a portable mount, but i am on the lookout for a more substantial mount to use with the refractor setup.

Initially i was drawn towards the William Optics ZS61 for its portability, and majority of good reviews. 

So onto the dilemma questions -

From a price point the TS photo line are appealing, but are they a step down in quality from the William Optics ZS scopes?

If i look at triplets (Sharpstar etc) would i be able to use it for visual as well as imaging?

Are high end scopes likes Takahashi FS-60CB worth the premium price over their WO/TS/Evostar ED equivalents?

All opinions gratefully received.

Dave.

 

[rl]

The usual advice is to focus on the mount first, since it will determine your total payload limit.. Do you need it to be portable? The HEQ5 has a brilliant reputation for doing photography with smaller scopes. It's portable in the back of a car, but not as Easyjet hand luggage. 

But to answer your question more directly...

The ZS61 is an excellent choice for widefield photography (I've had one) and it's really light at about 1.4 kg. . But you may find 60mm a bit limiting for visual . Fitting a finder can be awkward; a red dot on the DSLR hotshoe is a common solution. A better compromise may be something a bit bigger like the proverbial Skywatcher ED80. The extra few millimetres aperture do count in this range. Remember to budget for the field flattener. The really big argument in favour of the ZS61 is its airline portability. If you're not flying then maybe have a look at something a bit bigger...after you've looked at the mount!

I have  TS 65Q (no longer in production but there is something similar) which in my opinion has better build quality for AP than WO even if there is a lot less bling. Don't get me wrong; WO are very good but the TS65Q  was specifically engineered for AP; the flattener is included, the focuser is rigid rack-and-pinion and locks properly, the camera can be rotated easily to frame the subject. And there is a finder bracket. And the dewcap has a locking screw (lack of such is a pet hate of mine).

Triplets are better at colour correction than doublets but the difference with ED glass is small. The difference is more important with faster scopes; a big plus for a triplet is that it is possible to make fast scopes relatively colour-free. A GT81 triplet is f/5.9 native, compared to f/7.5 for an ED80 doublet which virtually halves the time for a given amount of exposure, assuming the reduced image scale is acceptable. But again, there are many excellent shots taken with doublets so I don't see any point in making a triplet an essential requirement. A good doublet is still an excellent AP choice.

Triplets are absolutely fine for visual. Some claim a good doublet will beat a good triplet on visual contrast just because there is less glass. This argument also trades on the fact that the eye is sensitive over a much small range of colours compared to a CCD, the more so as the light intensity goes down. Your eye peaks at about 500-550 nm wavelength whereas the camera can see 400 to 1000 nm at all levels of illumination.

In my opinion there is not much point in paying for premium brands unless you are a real perfectionist, but many will disagree.  Scopes like the Takahashi quad Petzval designs are wonderful pieces of engineering that will fill a massive sensor, but if you're using a humble APSC scale DSLR camera then a WO GT81 with flattener will do just fine. There is a convenience argument for a premium astrograph in that the flattener spacing adjustment is done for you and fixed. And because the flattener is built-in there is more flexibility in adding filter wheels, off-axis guiders.

You will find almost as many posts on flattener spacing as there are on Newtonian collimation...

Not all proper astrographs will allow you to use a 2" diagonal for visual, though 1.25" is usually ok. The TS65Q wont, nor the older Pentax SDHF75, though both will work with 1.25". I believe there are complications with the Tak quads on this score as well for visual. Make sure whatever you choose will do both, preferably with 2" diagonal. 

Hope this helps...

Edited August 4, 2021 by rl

[Nugs]

Really helpful thanks @rl especially the last para reference diagonal and EP's..... i has assumed (wrongly) that a 2.5" focusser would automatically accomodate a 2" diagonal for viewing.

I do intend on getting a dedicated cooled camera in the future (after i have sorted the mount) so i'm keen to make sure my scope choice is suitable as my experience and other equipment improves.

As a seasoned photographer, i do appreciate fast glass. Combine that with persistent cloud cover down here in the southwest, and i'm drawn more towards a fast triplet (https://www.firstlightoptics.com/william-optics/william-optics-gt-71-ii-2019-checked-tuned.html) that i can step down in focal length while i'm learning to capture the larger DSO's.

D.

[rl]

That would be an  excellent choice. 3kg...small and short, r+p focuser. It looks like a mini GT81 which has a good reputation. The focuser travel is enormous and should accomodate a 2" diagonal without issues for visual. And there is a customer return on offer....

[Sterrenland]

I initially started out using just a DSLR camera, then progressed to a Skywatcher 80ED with the DSLR and have finally very recently swapped the DSLR for a ASI294MC Pro.

I realise the SW 80ED may be just a little bit larger than you intended, but I can certainly vouch for it being a super 'little' scope, certainly for its price. It's not too unwieldy in size to make it a struggle to set up and its aperture has managed to bag some amazing sights for me. Yes, my processed pics aren't going to win competitions, but in the end most of us do this hobby out of sheer excitement at what you can 'see'. The scope that is the best for you will be the one you actually use. If it's tooooo heavy to carry...too complicated...requires too much maintainance...it'll end up being left indoors.

[Lee_P]

I use an Askar FRA400, which I find to be excellent for astrophotography. (I'm in the south-west too). Quite a forgiving instrument to use. It's bench-tested from FLO too, although stock levels tend to be quite low. I can't comment on its quality for visual use, but I expect it's good

 

[rl]

This review makes the Askar 400 look like the mutts proverbials for AP..in fact I'm very tempted myself..

However it makes little mention of the visual performance which is part of the op's requirement.  The FLO site makes the following comment:

Thus it's good visually for wide-field viewing. This is often a euphemism for "not good at high magnification". I might be overly suspicious but if the op is looking for an all-round instrument then this scope might be a disappointment on planets while excelling in its intended role for wide field AP. Owner input required!

[Lee_P]

11 minutes ago, rl said:

This review makes the Askar 400 look like the mutts proverbials for AP..in fact I'm very tempted myself..

However it makes little mention of the visual performance which is part of the op's requirement.  The FLO site makes the following comment:

Thus it's good visually for wide-field viewing. This is often a euphemism for "not good at high magnification". I might be overly suspicious but if the op is looking for an all-round instrument then this scope might be a disappointment on planets while excelling in its intended role for wide field AP. Owner input required!

I wrote that review 😁  It is a good choice for wide-field astrophography. I'd say that it punches above its price point, and its Petzval design and wide-field nature make it a forgiving instrument to use. More info and example photos are on my website. I haven't used it much for visual, but I'd say that your assessment is accurate: visually good for wide-field, but not designed for planets. It is a 72mm 400mm f/5.6 astrograph, after all.

[Nugs]

Apologies for the radio silence, currently away for a few days, and struggling to find a phone signal let alone 4G

Back on Monday, so will check in then, 👍

[CedricTheBrave]

i recently purchased one of these https://www.altairastro.com/starwave-80-ed-triplet-apo-travel-refractor-465-p.asp as a grab and go 

although i have not tried it for imaging yet I am very pleased with its visual performance