Would like to see Achro Refractor lunar/planetary imaging...

[emadmoussa]

Hola,

I've been Googling around for lunar/planetary images taken by 5/6" achromatic refractors in order to see the level of AC...Quite limited resources out there. It'll be nice if you can show yours.

I'm in the process of getting a 6" refractor and want to make sure of few things - most importantly is the level of achromatic aberration. Thanks to all the guys who gave me generous tips on pros and cons of fracs

Look forward to having a look,

Attached are a bunch of photos taken by high end achro refractors. The AC is not that significant even without filters.

Thanks!

Imad

[emadmoussa]

One more thing,

While searching it seems that refractors have more fans in the US than in Europe - or the UK in particular.

[allcart]

This would have been better placed in the Lunar imaging section Imad.

[emadmoussa]

Oh, OK. Mr. Mod, could you please move this thread to the Lunar imaging section? Thanks!

[Pig]

Its not moved yet

[emadmoussa]

OK, I'm gonna sit here cross-legged until it has been moved

[Pig]

Don't forget to tap your finger nails too

[JamesF]

I don't believe the CA is too bad with the longer focal length achromatic refractors I've seen people review whereas with, for example, the Skywatcher ST series it's painfully obvious. Perhaps the reason you don't see too much planetary imaging done with a long focal length achro is down to the pain of using them. A 120mm aperture 1000mm focal length refractor (say) is a hefty lump and long with it. By comparison a 5" Mak or SCT with more focal length and more compact design is probably going to give you an easier life all round.

James

[emadmoussa]

Well, I am thinking TS Individual 152/900...having searched around, regardless the price, seems like the best achromat of this size there is. The other equivalent, if cheaper, is the EXplore Scientific 152mm. The TS seems to score a bit better in terms of compact size and lenses. Not to mention, it's got a very nice 3" focuser. Above all has significantly less AC..nothing that cant be treated with a semi apo filter.

[foundaplanet]

I think if I was looking for a scope to image the planets and the moon I would be looking at getting a Mak. Thing is, if you really get taken by it you are not going to be happy unless you know you have the best you could get for your money and at nearly £700 your only £80 off a SW 180 pro. Also the TS frac is almost just over 11kg the 180 pro is 8kg a C8 is under 6kg both of which would give you better results on imaging SS objects.

Don't get me wrong fracs are great and I have an achro for visual with which the CA is of no issue to my eyes.

[JamesF]

I'm struggling to see a compelling reason to use that TS 152/900 scope for planetary and lunar imaging, to be honest. For about the same price there's the 150 Mak or C6 which give you pretty much the same aperture with a lot more focal length and no CA to speak of. Depending on the camera in use it's not uncommon to want four to five metres of focal length to give good image scale for planetary imaging and that's far easier to achieve with the Mak or SCT.

The idea of using a semi-apo filter for imaging really doesn't sit well with me either. The misaligned colour is not after all data that you don't want in your images such as IR might be, it's colour that you do want, but it's in the wrong place. Filtering it out is just getting rid of data that you ideally want to capture.

Obviously if you "just like refractors" then that's absolutely fair enough and there's no reason you shouldn't make that choice, but if on the other hand you want the best telescope you can get for imaging solar system targets for that money, I'd personally go for the Mak or SCT. If you did go down the refractor route then I might be tempted to suggest that perhaps RGB would be a better bet for planetary imaging. You would perhaps need to refocus between colours, but at least you'd be capturing all the data available.

James

[Stargazer_00]

JamesF makes all the right points in my opinion.

A fast achromat is possibly the worst tool for planetary imaging in my opinion. I'm sorry if that's sharp but that is my opinion. Pretty much any other scope would perform better. These scopes are designed for wide views of deep space objects.

A C6 would be so much better for planetary imaging being a decent focal length. And being an SCT it would be lighter than a 5" Mak too which means the mount would have to work less hard.

I just think you need to go into the purchase with your eyes well and truly open. If you do and you are happy with the choice then I wish you the best of luck.

I do own a 5" F5 achro and I can tell you it is the last thing I would choose to look at planets given a choice. They are small, bright and purple. The short focal length prevents you from ramping them up to a decent size and the CA kills the view. I accepted when I bought it (30th Jan) that it wasn't going to perform well on planets but I wanted a grab and go scope. I upgrade from an ST80 to the ST120, both very fast achros. Since Jan 30th the ST120 has pretty much be usurped already for a 6" newt as my grab and go. The newt offered more all round performance. Slightly less wide field but works well on planets, and moon and DSO. A great all round for the size.

My ST120 is now sitting in it's box and packaging in the loft waiting for the day I decide it's worth losing the money on to sell it on to someone who would actually use it.

[emadmoussa]

I totally see your points, guys. Apart from being a refractor person, like James says...which I am by the way I have never been happy or comfortable enough with reflectors. Neither have I ever been a keen Planetary observer or imager. I would like an SC or Mak, but I am frequently put off by their slow thermal stability. Yes, they are portable and great for planetary imaging, and I truly am considering a C9.25 or C11 having fulfilled my refractor desire first

I can't help it, I am just in love with the rich wide field crisp image of a frac. Stargazing00, I see where you're coming from. But I have to say an ST80 or st120 are great grab and go scopes, but drawing a comparison with the TS 152 probably not a fair play. Sufficient to say they are F5 achromats and unsurprisingly planetary viewing wasn't that satisfactory. I used my ST80 for casual visual observation when I first bought it. I liked it a lot. In fact, it was my intro to deep sky observing. Having moved to imaging, mainly DSOs, it took a back seat behind the 80ED as a guide scope.

I failed to mention that this scope will be majorly visual. If I am to image, considering its power, I will go lunar.

I have to admit though that there comes a time when you want to image planets...it's just the fluctuating nature of this hobby. I will then bite the bullet and get an SC or a Newtonian if I haven't already broken the bank.

[emadmoussa]

Oh, forgot to say...the decision is not final yet. I might have a change of heart at some point.

[JamesF]

Ah, well, if you're hooked on 'fracs then that's just the cross you have to bear In that position I might be tempted to start another thread asking people what their experiences are with CA on larger aperture short tube 'fracs rather than looking for images if you want good guidance on that. I can't help wondering if you won't always end up thinking "you know, the 200P just does this better". It's a lot of aperture to give away. Every scope has its compromises I guess. I've been very happy with my ST120 since I learned to accept its limitations and actually I struggle with the idea of parting with it because once in a while it's still my first choice of scope. The first time I saw M13 with the 10" dob had me dancing around the patio cackling like a witch though

James

[emadmoussa]

Well said, James. It really is about accepting the scope limitations. For visual I was happier with the ST80 rather than 200p. But almost always unhappy with Newtonian comfort factor and rather dispersed amount of light. Well, like I said, if the aperture fever strikes again..reflectors are not exactly an expensive option...if the Mrs of course allows more than 3 scopes sitting in the lounge

[John]

I thought I was a refractor only person but owning a string of 6" ones and then acquiring a newtonian with excellent optical quality has made me re-think a bit.

I've said this in other threads I think but I'd really think twice before shelling out £500+ on a large chinese achromat for imaging or visual. Sorry if it's a boring message - just trying to save you some £'s in the long run

[Stargazer_00]

It sounds to me like you are a man who knows what you want. I am a firm believer in saying my piece, and I have, but also in not pushing my opinion too hard either.

I wish you all the best and hope that the scope gives you everything you want I really mean that.

[emadmoussa]

OK, upon further research, it seems that the 125/5.9 telescope design has three different brand names (differences are in orange)

1) TS 152/900 (Individual Rich Field Refractor 152/900) from Teleskop Express Germany *** 3" Focuser (they call it: high class 3" focuser)

2) Astro-Professional 152/5.9 from Astro Professional Germany *** 2” aluminium Crayford focuser with 1:10 reduction + aluminum carrier suitcase

3) AstroTelescope 152/5.9 from Kunming United Optics in China and carried by its exclusive US dealer, Hands on Optics in Damascus, Maryland *** 2.5" Stellarvue R&P focuser

Having looked at the specs - the three scopes have almost identical features and I would bet the same type of optics. It's stated clearly that the AstroTelescopes version is manufactured in China, which at first sight seems like a turn-off. Even for me personally. Objectively speaking, the lack of trust in Chinese products appears to be a remnant from the past. Most high quality products now are outsourced to Chinese manufacturers for the sake of cutting down costs. These refractors, or at least the so-called Chinese version would've been more expensive if they were manufactured completely in Germany or the US. Plus, we all praise the Skywatcher and Celestron ED refractors, don't we? They're also manufactured in China.

Anyway, the AstroTelescops refractor aside since it's shipped from the US and will cost a fortune just for taxes and shipping. It's now narrowed down to the Astro-professional and TS Individual :

Astro-Professional: 1) £30 more in price but it comes with an aluminum suitcase (which is a good advantage) 2) 2" Crayford focuser

TS Individual 1) £30 less but no carrier suitcase 2) 3" advanced focuser

OK, I'm not sure what advantage a 3" focuser will give me. Is it worth it for £30 extra going for a 2" focuser and suitcase (Astro-Professional)?

I'd appreciate any thoughts

Thanks!

[Moonshane]

now moved as requested.

[fondofchips]

The theme here is that a scope is a personal choice. I followed the advice on here, but when I saw the large reflectors for real it changed my choice to a refractor instead. BUT of course there is no do it all scope so I knew that whatever I bought would be a compromise. I decided that a reflector was for some time in the future. The refractor is doing 2 jobs though as I will keep it as my mobile scope even when I decide to upgrade. I have the Lyra Optics F11 4" refractor made of aluminium so it's a bit lighter than most & the EQ5 mount which I also bought as my mobile scope support.

There is a lot to consider given the light levels & distances involved, which will always be part of the attraction & the challenge of Astronomy.

[Macavity]

Having compared Maks and ST's side by side, I was quite seduced by the *contrast* of the 'frac. But it was clear that, false colour aside, the ST102 objective was a lot "rougher" than the Mak127. As evidenced by the (absence of?) diffraction rings on one side of focus in the ST! That said, a crudely adjusted TS F4 Newt gives an ST a "run for it's money" and not in a good the best way! The latter does get better with tweaking and an 8" aperture has a lot of "grunt" power, despite the dodgy mechanics.

Something I have yet to try - Narrow band filters with an Achromat. For Lunar work, there is plenty of (reflected Sun) light. I want to try out my Baader "Solar Continuum" filter on the ST102 as a *video* setup. Of course it won't get rid of the spherical(?) aberration, the "surface roughness", but hope springs eternal...

[emadmoussa]

Sorry guys, is there a confusion between ST refractors and TS refractors?!

The TS refractor is the ''Teleskop Service''...ST refractos are the Skywatcher StarTravel series. Like I mentioned earlier, the TS is 152mm f/5.9 achromat while the the Skwatcher ST150 is f/5.5...so the the AC will be significantly different.

[Peter Drew]

I think you would have to go to F10 to see a significant difference in CA. For the same or near focal ratio, a 150 F5 achromat will have more CA than a 102 F5 achromat. I have a 102 ST and a 150ST, they both give great low power views but the CA at over 100X is significant. I also have an Istar 150 F10 and that shows an acceptable amount of CA. I'm not trying to influence the OP's decision but we were invited to give opinions.

[John]

Sorry guys, is there a confusion between ST refractors and TS refractors?!

The TS refractor is the ''Teleskop Service''...ST refractos are the Skywatcher StarTravel series. Like I mentioned earlier, the TS is 152mm f/5.9 achromat while the the Skwatcher ST150 is f/5.5...so the the AC will be significantly different.

There will still be lots of CA with an F/5.9 achro, who ever makes it, for the reasons Peter states above.