Binoculars vs Fast Refractor for Observing and CCD Imaging

[Tommohawk]

Hi All. I've posted here as the question covers multiple issues ... ie its a bit muddly! I'd be really grateful for any ideas on this.

I currently do DSLR imaging with SW200 and HEQ5 but have a few issues.

1. No widefield option

2. Fed up with limited breaks in the clouds

3. Unable to travel - if I had a light/small setup I could at least do something on holiday. Ideally airline cabin bag sized kit.

Also I will probably go for a CCD camera sometime, so here is the master plan, v1.0:

Get some 100mm bins. which would give nice portable observing option, + in theory I could attach a CCD camera to one eyepiece so it would double as a small refractor for imaging.

Keep the 200PDS, and use this for fast narrower field imaging and barlowed for planetary. A nice simple package which does everything.

Problem is, it doesn't seem possible to replace a conventional binocular eyepiece with a CCD - I posted re this in the binocular section and I think even if I could find a way of removing the EP and rigging an adaptor, I might not be able to reach focus - does that seem right? Especially as I want to do mono so would need room for filters.

If someone could confirm this or otherwise I'd be very grateful.

If that is so, then I could maybe get a binocular telescope with removable EPs like the Helios Quantum 5 - a lot more expensive though. And, even though it has interchangeable EPS, I might still have trouble getting focus with CCD and filter.

Any thoughts on that please?

Failing that, a short fast refractor. Because I aim to do narrowband, chromatic aberration shouldnt be too much of an issue (as I understand it, apart from maybe having to refocus between filters) so wide aperture is key, even if non APO/ED.

I wondered about the Startravel 102 - short, fast and inexpensive. But, according to some reviews not the best quality.

What do you think about that, or is there something similar that's better?

Thanks in advance for any input.

[Knight of Clear Skies]

Since you already have a DSLR why not simply put a camera lens on the front?

[michael.h.f.wilkinson]

I personally do not think I would like a double act like that. Bins do not usually have the level of CA correction needed for serious AP, and would be harder to mount equatorially. The ones that do have that levl of correction cost an arm and a leg (or maybe even a kidney). I would personally go for a decent pair of bins for grab and go (like the 15x70 Helios Apollo HDs I have) and a dedicated little frac for DSO imaging and the odd spot of wide-field observing (like the 80mm F/6 triplet I have as wide-field instrument next to the C8). You can get a 4" or even bigger ED APO starting from around 1,000 euro. By comparison an ED APO bin from APM sets you back three times that amount. That leaves a lot of dosh for focal reducers, or even a better focuser AND a pair of excellent binoculars.

[Tommohawk]

Since you already have a DSLR why not simply put a camera lens on the front?

Yes thats an excellent point, and one I'd considered. I was watching a 200mm F2.8 on *bay but it went up in price at the last moment! 

In any case, if I'm going to go CCD in due course, this isn't really helping. (I could get a DLSR lens to CCD adapter, but then I wouldnt have the observing option)

[SteveNickolls]

Hi, you could try something like this to hold a light camera to the eyepiece of your binoculars-http://www.amazon.co.uk/Baader-Microstage-II-Digiscoping-Adapter/dp/B002SYHDIS

I'd be unsure if removing the eyepiece from a binocular that has exchangeable lenses would work with a small camera replacing the eyepiece because of focusing issues but you never know. You would also have a potential problem with the binoculars remaining static as your object moved to contend with.

Best regards,

Steve

[Tommohawk]

I personally do not think I would like a double act like that. Bins do not usually have the level of CA correction needed for serious AP, and would be harder to mount equatorially. The ones that do have that levl of correction cost an arm and a leg (or maybe even a kidney). I would personally go for a decent pair of bins for grab and go (like the 15x70 Helios Apollo HDs I have) and a dedicated little frac for DSO imaging and the odd spot of wide-field observing (like the 80mm F/6 triplet I have as wide-field instrument next to the C8). You can get a 4" or even bigger ED APO starting from around 1,000 euro. By comparison an ED APO bin from APM sets you back three times that amount. That leaves a lot of dosh for focal reducers, or even a better focuser AND a pair of excellent binoculars.

Take your points. One advantage of bins though is that there a little shorter for the EFL, so fit in a flight bag better. I probably will have to go for a separate frac, but want to go as fast as possible, partly for super-quick imaging - maybe unguided - but also to keep the length down. The 102mm F5 startravel seems optimal and for narrowband imaging CA shouldnt be an issue - does that stack up? If the Startravel isnt great quality, is there a better F5 102mm that you know of?

[Tommohawk]

Hi, you could try something like this to hold a light camera to the eyepiece of your binoculars-http://www.amazon.co.uk/Baader-Microstage-II-Digiscoping-Adapter/dp/B002SYHDIS

I'd be unsure if removing the eyepiece from a binocular that has exchangeable lenses would work with a small camera replacing the eyepiece because of focusing issues but you never know. You would also have a potential problem with the binoculars remaining static as your object moved to contend with.

Best regards,

Steve

Thanks Steve. Consensus seems to be that removing a bin EP is asking for trouble. My existing cheapo bins certainly dont look to have enough travel. I could attach CCD to the EP as you say, but these clips dont look too solid to me, and the EP projection would lose field I think. Re tracking / guiding, if its superfast CCD I reckon I could do unguided on hols, and mount the bins to the guided HEQ5 at home.

[michael.h.f.wilkinson]

The problem of an ST102 with narrowband is that there are differences in focal length between the bands, so you would have to rescale the images subtly. Possible, but not ideal. I use my 80mm F/6 with 0.8x focal reducer (Tele-Vue TRF2008) at F/4.8 for imaging, so pretty fast, and airline portable. With an Amici prism and and a few Naglers (but no focal reducer) it is an awesome wide-field scope. The image is sharper than quality 15x70 bins can deliver.

[Peter Drew]

I would have a good read of "Making Every Photon Count" and then have a rethink. 

[michael.h.f.wilkinson]

One other thing to consider is that there all sorts of standard kit to attach a CCD or DSLR securely to a scope, and that there will probably be no issues with getting enough in-focus (especially a refractor with a large amount of travel on the focuser). Binoculars were not designed for this, so in-focus will probably not be sufficient, and getting adapters for them may be problematic. They will also cause problems with bigger chips, given the relatively small image circle the prisms provide. The prisms also reduce transmission, of course.

[Tommohawk]

Thanks Michael - I think I've given up on the idea of converting binoculars - in focus will definitely be an issue, and I hadn't even considered the issue of prism size.

Regarding the frac, I had considered the issues of refocus resulting form CA, but not the image size difference. 

That said, as a general point, it does seem that if NB imaging, you can get much more aperture for your £ if you don't have to worry about CA. And the resize issue isn't insoluble - once the maths is done it should be possible to batch resize. I guess then you'd lose the option for quality wideband which would be a bit of a shame.

The ED80 seems to have a tube length of 620mm, which I would think is a bit tight for a cabin bag, once packed nicely? Maybe that 620mm includes the extended focuser - maybe the front shroud can be unscrewed?

[michael.h.f.wilkinson]

I would have a serious look at the 80mm F/6 triplet scopes out there. More compact (420mm with dew shield retracted), better colour correction and faster. I have the predecessor of this one

http://www.teleskop-express.de/shop/product_info.php/language/en/info/p3881_TS-Photoline-80-mm-f-6-FPL-53-Triplet-SuperApo---2--Crayford-Auszug.html

Various other suppliers stock the same or very similar scopes under a variety of brandings

[happy-kat]

The member Gina did narrow band testing on the ST80 against a superior scope and the ST80 did well OK in the triple scope imaging rig.

Added the links as is narrow band using a star travel f5

http://stargazerslounge.com/topic/229147-st80-mods-for-imaging

http://stargazerslounge.com/topic/239097-400mm-focal-length-triple-scope-imaging-system/?fromsearch=1

[Scooot]

Hi Tom,My baby tak, fs60 is very portable and light, f5.9 so reasonably fast. Although not a triplet there isn't much CA, perhaps a tiny bit on the moon but hardly noticeable.I'm no imaging expert but the Star Adventurer I'm mounting it on handles it very well, so together they are a very portable package. Maybe however it's not enough aperture or a bit more than you wanted to spend. I didn't bother with the finder for it, as the fov is wide enough without it with my 24mm, which made it a bit cheaper. Thought I'd just bring it to your attention.

[Stub Mandrel]

There's a PrinzGalaxy 400mm at £15 buy it now on Ebay <edit> should have mentioned it takes a t-mount so can fit any DSLR. <edit again> The 'slight haze on rear element' affected my scope, I was able to get rid of this by removing it and gently cleaning.

http://www.ebay.co.uk/itm/PrinzGalaxy-Telephoto-Lens-/272026910527?hash=item3f56113f3f:g:ZtAAAOSwI-BWLRwh

I bought one of these second hand about thirty years ago (sure it was more than £15!)

This is a stack of 64 frames taken with it, 80 seconds , unguided EQ3 mount on EQ5 tripod. Don't think my cleaning had an adverse effect:

[Tommohawk]

I would have a serious look at the 80mm F/6 triplet scopes out there. More compact (420mm with dew shield retracted), better colour correction and faster. I have the predecessor of this one

http://www.teleskop-express.de/shop/product_info.php/language/en/info/p3881_TS-Photoline-80-mm-f-6-FPL-53-Triplet-SuperApo---2--Crayford-Auszug.html

Various other suppliers stock the same or very similar scopes under a variety of brandings

Funny I was looking for 80ED F6's and they dont seem to be that many around. The TS one does look nice though, and as you say just right for cabin bag - even Ryanair size!

I would have a good read of "Making Every Photon Count" and then have a rethink. 

Peter - Yes, thanks for that. I'm sure there are many good points in there that would be relevant.

The member Gina did narrow band testing on the ST80 against a superior scope and the ST80 did well OK in the triple scope imaging rig.

Added the links as is narrow band using a star travel f5

http://stargazerslounge.com/topic/229147-st80-mods-for-imaging

http://stargazerslounge.com/topic/239097-400mm-focal-length-triple-scope-imaging-system/?fromsearch=1

So - this seems to make the point about using a simple doublet for NB imaging. TBH theres no way i could compete with Gina for ingenuity, and the focusing issue does look a nightmare. That said, my current guidescope is an ST80, so maybe I should give it a go. I sort of forgot about that option!

Hi Tom,My baby tak, fs60 is very portable and light, f5.9 so reasonably fast. Although not a triplet there isn't much CA, perhaps a tiny bit on the moon but hardly noticeable.I'm no imaging expert but the Star Adventurer I'm mounting it on handles it very well, so together they are a very portable package. Maybe however it's not enough aperture or a bit more than you wanted to spend. I didn't bother with the finder for it, as the fov is wide enough without it with my 24mm, which made it a bit cheaper. Thought I'd just bring it to your attention.

Thanks for the idea. I guess thats a super scope, and nice f ratio. But not so keen on the mm aperture:£ ratio! I'd probably go for the TS 80Ed F6 on balance.

There's a PrinzGalaxy 400mm at £15 buy it now on Ebay <edit> should have mentioned it takes a t-mount so can fit any DSLR. <edit again> The 'slight haze on rear element' affected my scope, I was able to get rid of this by removing it and gently cleaning.

http://www.ebay.co.uk/itm/PrinzGalaxy-Telephoto-Lens-/272026910527?hash=item3f56113f3f:g:ZtAAAOSwI-BWLRwh

I bought one of these second hand about thirty years ago (sure it was more than £15!)

This is a stack of 64 frames taken with it, 80 seconds , unguided EQ3 mount on EQ5 tripod. Don't think my cleaning had an adverse effect:

Thanks for the tip - at £15 is does look to be a bargain!! However, I'm pretty committed to the CCD route so I think getting this would only be a temporary solution. Nice M31 though!

I think the conclusion is,

1. Give up on trying to do the double with binoculars.

2. Bearing in mind the results that Gina achieved with the ST80, and the fact that I will be switching to a smaller format CCD and thus avoid field curvature problems, I could get a small doublet type frac, but would have to live with the CA when observing or doing RGB imaging,

OR, get an 80Ed like the TS model.

I'm really very grateful for all the useful input. One final question. If I were to opt for the non ED route, the Startravel 102 does look a bit basic - only x1 speed focuser for example. Does anyone know of a better 100mm (or 102mm) F5 alternative? 

Thanks again.

[michael.h.f.wilkinson]

The TS scope is a triplet APO, which is why it can be faster than the SkyWatcher 80ED. There is a flattener for it, but I prefer using a focal reducer/flattener from TV with it.

[Scooot]

Found this. No idea where to get one or how much they are. Might be worth an email. There's also a 100mm f6.

http://www.longperng.com.tw/goods.php?act=view&no=7

[michael.h.f.wilkinson]

Interesting. I have seen quite a few achros of that spec (90mm F/5.5) but very few ED doublets

[Tommohawk]

Found this. No idea where to get one or how much they are. Might be worth an email. There's also a 100mm f6.

http://www.longperng.com.tw/goods.php?act=view&no=7

thanks for that - TS have them here. E1330 approx. 

Hadn't seen any 90mm fracs at all before - probably still get one in a flight bag.

But TBH this is a bit pricey, and, given the evidence that Gina has come up with re the viability of NB imaging even with a basic scope like the ST80, I'm still looking for an inexpensive non APO/ED 102 or 100mm F5 (or maybe F5.5) like the Startravel, but better quality focusser if possible. 

Any ideas?

[Tommohawk]

Oh thats the wrong link - should be this

[Tommohawk]

Well following on with the idea of NB imaging with a 90mm achro, I found two options which both have DS focuser:

The RVO 90 f500 and the Opticstar AR90 both look very pretty and get some good review for mechanics - though the optics seem to get variable reviews. I realise there will be CA and this is completely immaterial, so long as there arent excessive other aberrations.

Anybody got any recent first hand experience with either of these?

[lensman57]

Well you can not possibly do DSO imaging using binoculars or at least not the ones that are affordable to us mortals. For exploring the night sky there is nothing like a binocular but it has to be a good one. It can not be too heavy as to need some sort of contraption to keep it steady. You would want as large an exit pupil as possible to enhance  the vision and the light gathering must be good. In the old times ( a very long time ago ) I was always after a 8 x 56 but these are  a very pricy these days. A more reasonable offering is the Nikon Aculon  7 x  50. I have a Strathspey 15 X 70  which is good but very heavy and bulky.

As for the telescopes I am afraid that you get what you pay for. An ED doublet is an absolute minimum and Achros will not do for proper imaging. Besides the CA these budget scopes suffer from a multitude of optical aberrations . Get yourself a decent Wide Field ED to start with.

A.G

[Tommohawk]

Well you can not possibly do DSO imaging using binoculars or at least not the ones that are affordable to us mortals. For exploring the night sky there is nothing like a binocular but it has to be a good one. It can not be too heavy as to need some sort of contraption to keep it steady. You would want as large an exit pupil as possible to enhance  the vision and the light gathering must be good. In the old times ( a very long time ago ) I was always after a 8 x 56 but these are  a very pricy these days. A more reasonable offering is the Nikon Aculon  7 x  50. I have a Strathspey 15 X 70  which is good but very heavy and bulky.

As for the telescopes I am afraid that you get what you pay for. An ED doublet is an absolute minimum and Achros will not do for proper imaging. Besides the CA these budget scopes suffer from a multitude of optical aberrations . Get yourself a decent Wide Field ED to start with.

A.G

Thanks for that - yes I've given up on the idea of binoculars other than for observing.

It's a shame that nobody seems to produce a decent achro. The above offereings are £220, an ED/apo of the same aperture is > £1000. What did we do before EDs and Apos were around??

Also, it's funny that some folk seem to be doing OK with NB imaging using the ST80 - is this really that much better? Isn't there a comparable 90mm achro with DS focuser? Apparently not!

[lensman57]

Thanks for that - yes I've given up on the idea of binoculars other than for observing.

It's a shame that nobody seems to produce a decent achro. The above offereings are £220, an ED/apo of the same aperture is > £1000. What did we do before EDs and Apos were around??

Also, it's funny that some folk seem to be doing OK with NB imaging using the ST80 - is this really that much better? Isn't there a comparable 90mm achro with DS focuser? Apparently not!

Achros are a waste of time as far as imaging is concerned, forget about them. There are good ones but these have very long FL with F11~F15 and are mostly for lunar or planetary observing. As for the imaging scope please forget the aperture business, that is only relevant for observing. In theory a larger aperture will offer higher resolution but here in the UK with our weather, light pollution and less than ideal seeing at the best of times no real benefit will be had from  a high res system such as a TAK Epsilon but for shorter integration times. A good ED need not cost the earth SW 80 ED is a very well corrected ED doublet and can give some expensive triplets a run for their money. It is relatively slow but not by much and a reducer will give you a wider FOV. The focuser is nothing to write home about but with a bit of care and adjustment and so long as a huge CCD and FW is not hung from its back side it will function. You will also have change left from £500.00  to do other things with.

Regards,

A.G