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Adam J

Help me chose a Refractor to save up for ;)

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Adam J    584

Essentially I have decided that a new scope is on the horizon. Unlike some I have a preference for knowing what it is that I am saving up for, it gives me a goal I suppose. 

I have already decided that I am going to get a new camera also and that is going to be a QHY163m...probably. 

 

I currently use a 130PDS (650mm) @ F5 and a DSLR.

I find that the FOV on the 130PDS is ever so slightly too narrow for my liking. 

I have a friend with a Star 71(~350mm) and I find that his FOV is too wide for my liking, I want to resolve more detail. 

 

That has lead me to the conclusion that I want a focal length of around 550mm with the slightly smaller chip. I also want a scope that is at least as fast but preferably faster than my 130PDS at F5. However the 130PDS is a reflector and as such has a central obscuration meaning that at least 20% of the mirror is blocked and so the equivalent speed to a refractor is probably no faster than F6.25 equivalent. 

 

So in sum I am looking for a scope of around  550mm focal length of F6 or faster. I am also keen to get something with a good focuser as I have struggled with the one on my 130PDS, so that rules out the SW 80ED DS-Pro, I want something with better build quality. 

Also Note: 80% of my imaging will be narrow band. 

 

My immediate thought was that a Esprit 100 (550mm @ F5.5) would fit the bill perfectly, but my max spend is likely to be in the 1000 pounds range, so that's just not going to happen and the  Esprit 80 is just a little too short on focal length being used to 650mm

My current favorites are:

 

1) Altair Starwave 102 ED Doublet Refractor OTA 2017 Edition (uses FL53 glass as opposed to FL51 in the old version) 

102mm FL-53 Doublet, (714mm @ F7) and (571mm @ F5.6) with the 0.8x reducer corrector.  

http://www.rothervalleyoptics.co.uk/altair-starwave-102-ed-doublet-refractor-ota-2017.html

Comes in at just over 1000 pounds with the FF.

I like the look of the Altair astro focusers. 

 

2) Altair Starwave 80 EDT-R Triplet APO Refractor (A tripled with a Hoya FCD-100 ED element)

80mm FCD-100 Triplet, (480mm @ F6) used with a flattener only. 

http://www.rothervalleyoptics.co.uk/altair-starwave-80-edt-r-triplet-apo-refractor-ota.html

825 pounds with flatter. 

 

3) Maybe I should be going for the Esprit 80 after all? But it is over budget with the FF and probably a pre dispatch optical bench test from FLO and its starting to look like £1200....

 

Does triplet vs doublet really matter if I am mainly going for narrow band /  mono RGB imaging? Cant I just re-focus between filters? I have found some horror stories about cheap triplets that make me think that a doublet might be a better idea in my price range...makes me think that option 1 may be my best bet all in all. 

 

Any others that I should be considering? Or perhaps I should just be getting the moonlight focuser for my 130PDS....

 

Cheers,

Adam

 

 

 

 

 

 

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John78    174

Well you could buy the 80ED you discounted, and the properly paired flattener and a better focuser should you find the factory fitted one to be an issue and still be under budget and get known good equipment with a strong following, support and resale value and a properly flat field.

I tried a Altair FFFR on an 80ED and its a reducer sure - flattener not so much the stars at the edges on a APS-C sensor were awful.  I find the lack of serious data or serious imagers using any of the Altairs disturbing.

The esprit is a cracking scope by all accounts though.

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ronin    3,755

These days I would consider one of the ES triplets, everything they state as ED is actually triplet and not a doublet. The FCD-100 variants are the better. Bit unsure why but FLO no longer list ES scopes, sure they did.

If you are going to the US then A-T or Stellavue (think Stellarvue) have some nice sounding new offerings also. Unfoirtunatly there is no distributor in UK or EU.

Edited by ronin

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Jessun    353

Hi,

An ED80 is a real work horse. Especially for NB.

/Jesper

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Adam J    584
11 minutes ago, Jessun said:

Hi,

An ED80 is a real work horse. Especially for NB.

/Jesper

 

38 minutes ago, John78 said:

Well you could buy the 80ED you discounted, and the properly paired flattener and a better focuser should you find the factory fitted one to be an issue and still be under budget and get known good equipment with a strong following, support and resale value and a properly flat field.

I tried a Altair FFFR on an 80ED and its a reducer sure - flattener not so much the stars at the edges on a APS-C sensor were awful.  I find the lack of serious data or serious imagers using any of the Altairs disturbing.

The esprit is a cracking scope by all accounts though.

I discounted the SW 80ED due to what I consider to be a ropy focuser (same design as the 130PDS which I am familiar with) its also no faster than the 130PDS probably slower. The FFFR on the Altair Starwave 102 ED Doublet is matched to the scope I would hope it does better. I find the SW 80ED popularity to be more of a statement about its performance / cost ratio as opposed to its absolute build quality but you are correct its not the most popular brand.  

Edited by Adam J

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Jessun    353

The little ED80 with upgraded focusers rendered me 6 AAPOD in one year.

A Tribute to the Skywatcher ED80

 

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Adam J    584
15 minutes ago, Jessun said:

The little ED80 with upgraded focusers rendered me 6 AAPOD in one year.

A Tribute to the Skywatcher ED80

 

Great images.

Like you say you upgraded the focuser. I would just rather buy a scope that I dont instantly have to start taking apart. I would also rather have a faster scope if I can as we get so few clear nights in the UK. The total exposure on those images in a single year could never be achieved from my location.

 

Edited by Adam J

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Jessun    353

I see what you're saying of course, but in the world of no free lunches, the ED80 is at least a free starter in terms of the lens. For some reason it hit the jackpot for the price range.

Good luck hunting!

/Jesper

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newbie alert    216

The 80ed is a awesome scope for the money.. the esprit  is prob the next stage up .

You can't have a faster f ratio unless you shorten the focal length

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Louis D    888
28 minutes ago, Adam J said:

The total exposure on those images in a single year could never be achieved from my location.

Go with a slower scope in a remote controlled observatory on a desert mountain somewhere. :laugh2:

Seriously, a lot of advanced imagers are going this route.

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Uranium235    6,086

If you really want to take your images to the next level, get a dedicated mono camera instead ;)  It will do far more for you than a new telescope would.

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Adam J    584
7 minutes ago, Uranium235 said:

If you really want to take your images to the next level, get a dedicated mono camera instead ;)  It will do far more for you than a new telescope would.

Hence the QHY163m I mentioned above. ;) That along with the moon light focuser for the 130PDS is another option and get a refractor later down the line. The only thing making me hesitate is that the FOV will be even more marginal than with the APS-C sensor, hence wanting a shorter focal length scope. Also the QHY163m and a filter wheel and a focuser upgrade for the 130PDS is way more cash than my budget for a scope.

Edited by Adam J

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Jessun    353
13 minutes ago, newbie alert said:

You can't have a faster f ratio unless you shorten the focal length

This is not so. Just keep the focal length and open up the aperture, either by a bigger lens or a mirror.

/Jesper

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Uranium235    6,086
1 minute ago, Adam J said:

Hence the QHY163m I mentioned above. ;) That along with the moon light focuser for the 130PDS is another option and get a refractor later down the line. The only thing making me hesitate is that the FOV will be even more marginal than with the APS-C sensor, hence wanting a shorter focal length scope.

Well, with the massively increased sensitivity over your current camera you will be spending less time getting to an acceptable level, which means you can spend the time you would have taken with the DSLR on doing mosaics - that is where your increased FOV will come from. Plus, once youve strapped together a few panels you can resample downwards by 20% in order to reduce the noise even further - but retain quite a large image size.

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Adam J    584
2 minutes ago, Jessun said:

This is not so. Just keep the focal length and open up the aperture, either by a bigger lens or a mirror.

/Jesper

Exactly hence my interest in the 102.

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newbie alert    216
16 minutes ago, Jessun said:

This is not so. Just keep the focal length and open up the aperture, either by a bigger lens or a mirror.

/Jesper

Yes this is true..focal length divided by aperture equal focal ratio..but what scope has a f5 ratio with a long focal length that's different to what he already has?

Unless it's a f2.8 epsilion 

Edited by newbie alert
Added info

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Adam J    584
8 minutes ago, newbie alert said:

Yes this is true..focal length divided by aperture equal focal ratio..but what scope has a f5 ratio with a long focal length that's different to what he already has?

Unless it's a f2.8 epsilion 

The 130PDS is F5 but its speed is not equivalent to an F5 refractor due to the secondary mirror blanking the primary. Its probably more like a F6.3 in refractor terms. So anything less than F6.3 should be faster than my 130PDS. 

Like i said my ideal would have been a Esprit 100, its just very expensive by my standards.

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25585    194

A shame the Tele Vue TV-76 is outside your budget. They do appear on ebay occasionally. 

 

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