Startravel ST102T for White Light Solar Imaging?

[ArmyAirForce]

Much as I'd like an ED80 as an all round imaging scope, funding isn't going to cover that without resorting to selling a lung.

So I've been pondering buying the Startravel ST102T ( f4.9 Refractor ) as more managable size scope for White Light solar imaging, rather than my S/W 200PDS reflector. At £160.00, the ST102T is just about affordable ( after I've also bought an Astronomik UHC filter for my Canon!! ).

I know it has CA issues, but I'm hoping that shooting mono with Baader film and a UV/IR block and Solar Continuum filter will mean that the CA isn't a problem. It would also make a nice travel scope to view with or take less serious 'happy snaps' pictures when away.

So what are your thoughts. Would the ST102T make a reasonable white light scope?

[Ant]

CA won't be an issue.

These were taken with a ST102 and dmk21.

Cheers

Ant

[nightfisher]

You wont get any CA on white light, Moonshane got an ST120 for white light and found it superb, go for it

[astrorabbit]

Yep, I use it with the Baader solar film. It's also my guidescope

I have the Celestron version whilst a friend has the SW. They are identical apart from branding.

<a href="https://www.flickr.com/photos/mattpie/14144970484" title="First Solar Attempts by Matthew Pierzchala, on Flickr"><img src="https://farm6.staticflickr.com/5111/14144970484_a0e06f6bd2_q.jpg" width="150" height="150" alt="First Solar Attempts"></a>

[Steve Ward]

It would be OK , my ST120 was OK ...

Not a patch on the Tal 100RS though , worth saving a bit more for in my opinion ... 

[ArmyAirForce]

The Tal is less of a travel scope though, being a metre long.

[JamesF]

I certainly accept that the images above show little sign of CA, but surely it's not true that you don't get CA with a white light filter?  All it does is chop a huge amount of the light out across the entire spectrum, whilst leaving the remaining fraction (of the entire spectrum) to pass through (otherwise you'd not see the image as white).  If you have the entire visible spectrum passing through the optics then if you get CA without the filter you'll get it with.  If you have the solar continuum filter as well then I'd agree that should resolve the problem by removing much of the spectrum that causes the trouble.

Based on Steve's images and Ant's above, I'd certainly agree that the ST102 would do a reasonable job.

Alternatively you might perhaps consider one of the smaller Maks or SCTs.  Probably far more awkward to use a continuum filter with, but if you're looking at it as a portable scope then that may make a difference.  In my case we're usually driving so it's no big deal to stick the Mak in the car.  If I were flying I'd probably want the ST102.

James

[ArmyAirForce]

Diameter is more of an issue. For portable, I want something that will go in the car with a wife, child and all the luggage that is included. A small diameter refractor will pack better than a large SCT tube. I'f I'm just going to a dark site on my own, I take my 200PDS.

[JamesF]

There's a 102mm Mak, too.  No idea how it would compare to an ST102 overall though.

James

[Steve Ward]

A small Mak would be a very good choice , my ETX105 gives superb views in whitelight , the only reason I don't use it for imaging is the focuser , which is too much of a faff to motorise and USB control.

[Gina]

A narrow band filter will certainly get rid of any CA - I'm using ST80s for NB imaging and getting pinpoint stars   Though you won't need the expensive Astrodons that I use for DSO imaging - I would think the cheapest Baader Ha CCD filter (35nm) would do a pretty good job and give you nice sharp images.

[ArmyAirForce]

Thanks, I've been watching your thread with interest.

[ArmyAirForce]

Every so often, life throws a curved ball you don't expect, and today, I sold one of my old model aero engines for a little over a couple of hundred pounds, out of the blue. This now brings an ED80 about within budget. While a smaller diameter, it will have better optics than the ST102, so would the better optics and slightly longer focal length make up for the slightly smaller diameter?

This would give me a much better scope for travel imaging, and still a nice compact size for solar.

Thoughts? Would the ED80 make a better choice.

[JamesF]

The resolution will be reduced thanks to the smaller aperture, but I think the definition should certainly be better with the higher quality optics so that might balance out.  The ED80 is noticeably longer than the ST102 though.

James

[ArmyAirForce]

There is only 100mm difference in focal length ( plus whatever difference there is in focusser etc ), but that doesn't pose so much of a problem. It's mainly that my 8 inch reflector takes up so much room in the car if the family are heading over to the in-laws static caravan at the lakes. Lovely dark sky, and with a wife and child, neither of whom pack light, bulk is an issue. The lengh difference between the ST102 and ED 80 is minimal, compared to a metre long Tal 100RS, or the metre long 200mm diameter reflector.

[Gina]

The ED80 is a very good performer

[james_screech]

Is the focuser really up to imaging requirements though?

[Gina]

Depends what you want to hang on it.  The standard focuser is decidedly poor.  I replaced mine with a Baader SteelTrack.

[ArmyAirForce]

Well it now looks more likely that I'll be buying an ED80, rather than the ST102.

[Moonshane]

My 120mm sw provides noticeably more detail on the sun than my 80mm f11 vixen. The latter is not quite ed level but close. I use a lunt wedge with baader sc filter and a polariser.

[spaceboy]

I'm no imager but for solar I don't think it would make all that much difference. I was under the impression that achromatic refractors were favoured towards green light so in theory would this not help when combined with SC filters ??? again I'm no expert on this and others may be better informed on this.

If it was my choice the ED would always win as it's not just about CA when buying a better lens.