Refractor for Imaging

[kon1966]

Hi guys, I have a 8se and looking at buying a refractor for wide field imaging to use on the 8se mount. Putting aside that it is a Alt/Az mount and limitations, I do find it easy to setup and starsense accessory works like a charm.

Triplets are very expensive and heavy so I have found a sky watcher 600 x 120 f5 which is lighter than my celestron sct8 and not exensive and competitively priced and I can get it in Sydney OTA only for $499. I also will want to use my 2 inch diagonal.

Has anyone have had ant experience in imaging with this scope.

Regards
Kon

[PRejto]

I must be missing something, but how would you image with a non-equatorial mount? I guess you could use a field de-rotator. Is that what you are thinking?

Peter

[kon1966]

Hi Peter,
do not use a derotator and ideally as eq mount is preferred. I limit my exposure to max 30 secs due to heavy light pollution and use a eos 1100d with eos clip.. I do have some good success though and I do amaze my friends.

Regards
Kon

[Slawomir]

Hi Kon,

This particular telescope might be quite good for narrowband imaging, but I feel it would not perform very well for RGB imaging or with a dslr. Also, a diagonal will potentially introduce a few gremlins (tilt and flex) so I would avoid using one for imaging.

[Atmos]

As long as you don't go over 30s you can get some pretty reasonable shots with a short focal length.
I do agree with Suavi, it is MUCH better to use with narrowband imaging than with the RGB of your DSLR.

The main reason that triplet refractors are so expensive is because they are very well colour corrected, with a cheap 120x600 F/5 refractor, you will get some really strange star halos! It is not noticeable with narrowband (I had personally considered getting a 150/750 cheap refractor for that exact purpose :)

I have at one stage tested imaging through a diagonal, not a good idea. It adds some strange artefacts into your images.

[Barnacle]

Hi Kon,

Links below are 3 users review of the sky watcher 600 x 120 f5

http://www.cloudynights.com/page/articles/cat/user-reviews/telescopes/120mm-130mm-refractors/skywatcher-120mm-f5-refractor-r1552


http://www.cloudynights.com/page/articles/cat/user-reviews/telescopes/120mm-130mm-refractors/synta-skywatcher-120mm-f5-achromatic-refractor-r472

http://www.cloudynights.com/page/articles/cat/user-reviews/telescopes/120mm-130mm-refractors/skywatcher-120600-short-tube-achromatic-refractor-r1980

Hope you find these reviews useful.

Kind regards,

Bill

[kon1966]

Thanks guys for advice.

[doppler]

Here's a link to a recent thread about imaging with fast achro's. The CA can be bad on bright stars.

http://www.iceinspace.com.au/forum/showthread.php?t=144540

[Max Vondel]

I had the 120mm F5
Terrible chromatic aberration my advice stay clear of it

[glend]

You can shoot narrowband with your dslr, however it requires a mono conversion, and preferably cooling, to be most effective, and something to easily change filters, like the Teleskop-express EOS filter drawer. As your just starting out, i would recommend just shooting normal colour with your current camera, least risky, and put your money into a scope that provides true colour rendition. The most cost effective aperture, that provides true colour rendition, would be something like an 8" imaging newt. It will cost a fraction of a colour corrected refractor, but requires a rethink about your equipment priorities, and the money saved can be directed into a second hand EQ mount like an HEQ5 which could drive an 8" newt.

If you really want to image with a cheap achro refractor, then buy a ZWO ASI mono camera (they are cheap but provide a starting point). That camera would allow narrowband imaging. But the gotcha in narrowband is the cost of the filters and the requirement for long image exposures, so you need good EQ tracking and guiding capability. Which brings us back to the mount. If your serious about imaging you will need a good EQ mount.

[Amaranthus]

I was out last night doing some testing with a SW120 at f/4 (focal reducer attached). I'm currently using it as a guide-scope for a piggy-back mounted wide-angle lens. Guiding camera is a ZWO ASI120MM as mentioned above by Glen.

Attached are single-frame mono images of the Jewel Box (5 sec exposure) and Omega Centauri (10 sec) - purely for demonstration.

I also have some more 'serious' shots I took with the SW120 and an Orion G3 CCD, using NB (quite good!) and RGB filters (not so good...). Mixed results!

Skull nebula (NB): http://www.astrobin.com/125368/
Helix nebula (NB): http://www.astrobin.com/135036/D/
Orion nebula (NB): http://www.astrobin.com/127280/B/

NGC6940 Open Cluster (RGB): http://www.astrobin.com/125603/
M33 (low to horizon, RGB): http://www.astrobin.com/126583/B/

Stars suffer from bloating in RGB, especially the blue channel. But with persistence you cab do okay with this setup, especially in Narrowband as mentioned above. Good luck if you try it!

[Atmos]

Semi decent narrowband filters on a 150/650 achromat can be wonderful.

http://www.iceinspace.com.au/forum/showthread.php?t=23971

[skysurfer]

There can be an option in-between an expensive A$2500 10cm triplet and a A$400 12cm f/5 achro.

I have a TS ED110 (same as Astro Professional or Stellarvue, all from Kunming Optics) f/7 I got it second hand for E$700 (new E$1100, about A$1500 at TS in Germany) and it is a really nice scope, Lightweight (I let it lose some extra weight), about 4kg for the OTA.
Suitalble for photography and visual use as well. I took it with me on a recent South Africa trip.

http://skysurfer.eu/AP110.php

[Slawomir]

I totally agree. My TS ED102 f/7 doublet with a reducer has proven to be a quite capable scope (and relatively fast) for narrowband imaging :)