Best DSO astro-imaging refractor for around £1k?

[Zadoq]

Hi,

After a bit of planetary and lunar imaging, we'd like to move on to deep sky imaging.

What do you think is the best scope to get with a budget of around £1k (£1200 at a stretch)? It would be our first refractor, so an all-rounder DSO imager would be best if there is such a thing.

Having had a look at the scopes on the FLO web site, the following 2 drew my attention:

• Skywatcher Esprit 80 ED PRO Triplet
• William Optics GT-81 Triplet Refractor

Are there any others I've overlooked?

I thought it would be best looking at triplets rather than doublets.

Is there a sweet spot regarding the focal range? I have no experience how much space the DSO will take in an image. I appreciate there are some very big ones and some very small ones, but typically I've seen focal length of around 400mm to around 1000mm, with the more expensive ones generally being between 400 and 600mm. Is there a focal length range that could be considered an all-rounder?

Another way of putting this is: if you could only have one refractor for DSO's which focal length would you prefer?

Similar question for focal ratio. I know the faster the better, but also the most expensive, so at which point does the focal ratio start being too low because not very good optics are being used?

Finally, I would also be interested in the amount of back focus and whether you'd think, in your experience, whether it would be sufficient to eventually fit a filter and maybe a focuser and an OAG. (I've gone through a very interesting thread from Gina who was testing the SW and ran into back focus issue when she wanted to fit her OAG)

Anything I should be looking out for / paying attention to?

Thanks in advance for your input

Nico & Carly

[swag72]

Do you have a mount already? I ask as this really is THE most important part of the AP setup. You make no mention of a mount, so I assume that you have one?

[Zadoq]

Do you have a mount already? I ask as this really is THE most important part of the AP setup. You make no mention of a mount, so I assume that you have one?

Yes, that part is sorted-ish.

We currently have a Celestron Advanced VX. There was a question mark over it by a member about auto-guiding and how apparently it cannot correct error in DEC, but I've had confirmed that it is not the case. I'm in the process of double-checking.

If it can correct in DEC, we're likely to keep it for now as it appears to be quite a good, steady mount.

If it cannot then we'll replace it with a NEQ6.

Even if we have to keep the AVX for now, I'd like to assume a NEQ as I'm sure we'll upgrade to that mount at some point

Thanks

Nico

[nmoushon]

I personally would go with the SW. There are several people on here already that could help you with this one if there is any trouble.

In regards to FL you need to decide on what you want to image. If you want nebula then I would go with a shorter FL (Dont forget you can add reducers to give you a more suitable range). Galaxies will require longer focal lengths and that is what will really eat up your budget. The longer the FL the larger the aperture the higher the price. Especially for triplets.

Different tragets also require different speeds. For galaxies you can get away with a bit slower speed like F/7-F/10 (Like with the SCT EdgeHD). But for faint nebulas you will want faster speed like F/4-F/6. Just remember if you go too fast with a cheaper scope you will like induce unwanted color abberation. This is more prevelant in doublets where triplets tend to be able to correct for this. Like the Tak FSQ85 can drop down the F/3.75 if I remeber right. If I tried that with my doublet you would think I was imaging with an Achro refractor lol.

I'm sure someone else will pipe in with better information than I can give.

[lensman57]

Hi,

After a bit of planetary and lunar imaging, we'd like to move on to deep sky imaging.

What do you think is the best scope to get with a budget of around £1k (£1200 at a stretch)? It would be our first refractor, so an all-rounder DSO imager would be best if there is such a thing.

Having had a look at the scopes on the FLO web site, the following 2 drew my attention:

• Skywatcher Esprit 80 ED PRO Triplet
• William Optics GT-81 Triplet Refractor

Are there any others I've overlooked?

I thought it would be best looking at triplets rather than doublets.

Is there a sweet spot regarding the focal range? I have no experience how much space the DSO will take in an image. I appreciate there are some very big ones and some very small ones, but typically I've seen focal length of around 400mm to around 1000mm, with the more expensive ones generally being between 400 and 600mm. Is there a focal length range that could be considered an all-rounder?

Another way of putting this is: if you could only have one refractor for DSO's which focal length would you prefer?

Similar question for focal ratio. I know the faster the better, but also the most expensive, so at which point does the focal ratio start being too low because not very good optics are being used?

Finally, I would also be interested in the amount of back focus and whether you'd think, in your experience, whether it would be sufficient to eventually fit a filter and maybe a focuser and an OAG. (I've gone through a very interesting thread from Gina who was testing the SW and ran into back focus issue when she wanted to fit her OAG)

Anything I should be looking out for / paying attention to?

Thanks in advance for your input

Nico & Carly

Hi Nico,

I'd go for the WO, I have the ZS71 doublet and the focuser alone is worth the asking price IMHO as it is a sort of R&P Crayford type and once adjusted it really does not move even with a CCD, FF/FR and a filter wheel. The AVX is more than capable of carrying the whole lot with ease.

Regards,

A.G

[Zadoq]

1 all 

@ lensman57 Do you know if there is a good William Optics member base at SGL? One thing that I would like to take into account is the support I would get if I had specific questions related to a setup with that scope

Thanks

[Sp@ce_d]

My quick answer would be the Esprit 80 on optical quality for a triplet. However, I've been tempted to get an 81 to compare as I prefer the WO "fit and finish" it's just that my 80ED beats all the doublets I have for RGB so would that be the case for the. 81 triplet? I'd like to know...

Sent from my iPhone using Tapatalk

[lensman57]

1 all 

@ lensman57 Do you know if there is a good William Optics member base at SGL? One thing that I would like to take into account is the support I would get if I had specific questions related to a setup with that scope

Thanks

I know a few who use the ZS 71, but that is mainly for NB imaging. There is a member with a new GT81 and he has written a very good review of this scope with the good and the bad points, here is the link.

http://stargazerslounge.com/topic/203720-william-optics-gt-81-review-part-2-and-first-light/

Regards,

A.G

[lensman57]

My quick answer would be the Esprit 80 on optical quality for a triplet. However, I've been tempted to get an 81 to compare as I prefer the WO "fit and finish" it's just that my 80ED beats all the doublets I have for RGB so would that be the case for the. 81 triplet? I'd like to know...

Sent from my iPhone using Tapatalk

I would agree with you regarding the ED80 being very well corrected for a doublet, and I do like using mine but it is also 2/3 of an F stop slower than most other doublets at F6 or thereabouts. The Esprit 80 is already at a super fast F5 so unless the optics are of super premium quality then I guess the performance will be the same. I had my eyes on the Esprit for a while but some of the reported problems with the pinched optics and the focuser made me to wait untill a more representative sample of opinions have been expressed. The other point is that the WO GT81 including the FF/FR is about £830.00 so it will leave enough change for either a clip filter of some sort for the DSLR and perhaps even a 50mm finder guider, the guide camera is another matter.

regards,

A.G

[Zadoq]

Thank you all for your comments. After some more reading regarding those 2 scopes, we have decided to go with the WO GT 81. I'm certain that the SW is a pretty good scope too, but hopefully we will be returning amongst the crowd of WO owners who love their scope (and some decent images - I'm sure if they're not, it'll be our fault)... 

Carly & NIco

[ollypenrice]

You can model your imaging setup on the sky in most planetarium packages and doing so is an essential part of imaging. I do it in Chris Marriott's SkyMap Pro out of habit but I think you can do it in the free Stellarium.

The only variables are focal length and chip size, which you plug in. Then it will give you a box the size of your image to sit over the map of the sky. This tells you whether to frame in landscopae or portrait and what will fit.

A tip; try to image in landscape or portrait and not at arbitrary angles (though sometimes you have to.) It makes returning to an object much, much easier on future occasions. To set the camera along the lines of RA and Dec is easy; take a three second sub while slewing in either RA or dec, but not both. This will create star trails. When these trails are horizontal or vertical you are orthogonal with RA and Dec. Finding an arbitrary angle again when reframing is an incredible time waster!

Olly

[Ewan]

Hi,

After a bit of planetary and lunar imaging, we'd like to move on to deep sky imaging.

What do you think is the best scope to get with a budget of around £1k (£1200 at a stretch)? It would be our first refractor, so an all-rounder DSO imager would be best if there is such a thing.

Having had a look at the scopes on the FLO web site, the following 2 drew my attention:

• Skywatcher Esprit 80 ED PRO Triplet
• William Optics GT-81 Triplet Refractor

Are there any others I've overlooked?

I thought it would be best looking at triplets rather than doublets.

Is there a sweet spot regarding the focal range? I have no experience how much space the DSO will take in an image. I appreciate there are some very big ones and some very small ones, but typically I've seen focal length of around 400mm to around 1000mm, with the more expensive ones generally being between 400 and 600mm. Is there a focal length range that could be considered an all-rounder?

Another way of putting this is: if you could only have one refractor for DSO's which focal length would you prefer?

Similar question for focal ratio. I know the faster the better, but also the most expensive, so at which point does the focal ratio start being too low because not very good optics are being used?

Finally, I would also be interested in the amount of back focus and whether you'd think, in your experience, whether it would be sufficient to eventually fit a filter and maybe a focuser and an OAG. (I've gone through a very interesting thread from Gina who was testing the SW and ran into back focus issue when she wanted to fit her OAG)

Anything I should be looking out for / paying attention to?

Thanks in advance for your input

Nico & Carly

Had the same descision a while ago & after weeks of deliberation, questions & browsing i went with the Altair Astro EDT 80mm, you will find everyone has their favourites but do your homework & go for what you feel will suit you best & what you want to image. I am sure every scope manafacturer will let a 'bad' one slip through now & then so dont base your choice on a single review, as you have already chosen one i hope you enjoy your new kit & have many fruitful outings.

You can model your imaging setup on the sky in most planetarium packages and doing so is an essential part of imaging. I do it in Chris Marriott's SkyMap Pro out of habit but I think you can do it in the free Stellarium.

The only variables are focal length and chip size, which you plug in. Then it will give you a box the size of your image to sit over the map of the sky. This tells you whether to frame in landscopae or portrait and what will fit.

A tip; try to image in landscape or portrait and not at arbitrary angles (though sometimes you have to.) It makes returning to an object much, much easier on future occasions. To set the camera along the lines of RA and Dec is easy; take a three second sub while slewing in either RA or dec, but not both. This will create star trails. When these trails are horizontal or vertical you are orthogonal with RA and Dec. Finding an arbitrary angle again when reframing is an incredible time waster!

Olly

Good advice there from Olly, i learnt the hard way, attach camera & start shooting [removed word] nilly

The other thing is when using Artemis you can place 'markers' on stars in your sub & save it as a txt document, this then lets you load that same document on your next session, line up the stars to the 'loaded' markers & away you go, the 180 degree flip option is also very handy, best have a practice first before the real thing so valuable imaging time is not wasted.

[swag72]

I'm sure that the WO will be a good scope - certainly the one I would have picked between the two you mentioned in your OP.

£1k is an odd budget - It sounds like a fortune, but in reality, it doesn't get you as much as you think that it should.

[dmahon]

I'll watch with interest, as those two scopes are on my list to (together with Takahashi, although that's going to be harder to sneak past her indoors).

The 81 is probably top of the two for me - slightly faster and cheaper to boot.

[ollypenrice]

I'll watch with interest, as those two scopes are on my list to (together with Takahashi, although that's going to be harder to sneak past her indoors).

The 81 is probably top of the two for me - slightly faster and cheaper to boot.

Buy the Takahashi. No sane person would ever believe the price. If an enemy betrayed you, you could hold it up and say, 'That, three and a half grand, don't be ruddy daft!' and you'd win...

Olly

[dmahon]

I've got away with the observatory and all the ancillaries, don't want to push my luck!

[dmahon]

Well, not yet

[Zadoq]

You can model your imaging setup on the sky in most planetarium packages and doing so is an essential part of imaging. I do it in Chris Marriott's SkyMap Pro out of habit but I think you can do it in the free Stellarium.

The only variables are focal length and chip size, which you plug in. Then it will give you a box the size of your image to sit over the map of the sky. This tells you whether to frame in landscopae or portrait and what will fit.

A tip; try to image in landscape or portrait and not at arbitrary angles (though sometimes you have to.) It makes returning to an object much, much easier on future occasions. To set the camera along the lines of RA and Dec is easy; take a three second sub while slewing in either RA or dec, but not both. This will create star trails. When these trails are horizontal or vertical you are orthogonal with RA and Dec. Finding an arbitrary angle again when reframing is an incredible time waster!

Olly

That's very good advice, thank you. I was wondering how people, with integration times above 12 hours, managed to exactly go back to where they were and carry on.

Nico

[Zadoq]

The other thing is when using Artemis you can place 'markers' on stars in your sub & save it as a txt document, this then lets you load that same document on your next session, line up the stars to the 'loaded' markers & away you go, the 180 degree flip option is also very handy, best have a practice first before the real thing so valuable imaging time is not wasted.

Thanks, I'll keep that in mind too

Nico

[dmahon]

Plate solving and automated GOTO. SGP usually puts me within a few pixels.