[SOLD] Tal200K

[swannies1983 (Dan)]

I'm reluctantly selling my Tal200K scope which I purchased secondhand while I was in the US in 2006.

Details:
Aperture: 200mm
Focal length: 2000mm
Weight: 12kg for the OTA (it's a beast so a decent mount is needed!)

A bit of information about this scope:

The TAL-200K provides an aperture of 200mm and focal length of 2000mm in a very compact tube length of only 550mm (22 inches). Klevtsov's revolutionary catadioptric design employs a sub-aperture meniscus correcting lens (like the familiar Maksutov) combined with a Mangin mirror-lens secondary. Its fast focal ratio of f/10, flat field, and excellent correction of coma, spherical aberration, and astigmatism (14 micron star images at a distance of 10mm from the optical axis!) make the TAL-200K a superb instrument for astrophotography, far surpassing conventional Schmidt-Cassegrain and Ritchey-Chretien systems.

A detailed review can be seen here which confirms the Tal200K competes well against Ritchey-Chrétien systems.

I had planned to image with this scope but a few problems initially presented itself. The Tal comes with a 1.25" R&P focuser which certainly isn't the greatest. There are several discussions about changing the focuser to a 2" one, enabling one to undertake imaging. Some problems: 1) the 1.25" focuser is actually connected to the back plate. An entirely new back plate with a SCT thread is needed to allow one to use a 2" focuser and 2) a very low profile focuser is needed to allow focus to be achieved when using a diagonal* in combination with 1.25" eyepieces. From what I have read, there's not enough IN focus when using 2" eyepieces.

*when using the supplied Tal 1.25" diagonal

My modifications:
1) A new back plate with SCT thread
2) New extra low profile focuser made by Crawmach (see here. Focuser towards the bottom of the page).

Other people have done similar modifications but have had to move the primary mirror to allow enough IN focus when using a diagonal and 1.25" eyepieces following this modification. The good thing about my modification is that I have not had to move the primary to achieve focus with all my eyepieces when used in combination with the Tal 1.25" diagonal. I can't guarantee this will be the case with other diagonals.

Now, to the imaging side of things. The above focus issues are only relevant when using a diagonal. There are no problems with a straight through configuration. The focal point is ~44mm from the top of the focuser to the front of my modded canon 30d camera. I have only had a brief chance to try out imaging with this setup (see the attached Eta Carinae image). I had no time to polar align and there was no autoguiding. It's a combination of 5x30sec subs @ ISO1600 with a modded 30D. No cropping has been done. The main issue is a bit of field curvature.

The next step is to get a focal reducer. This is something I have done a bit of research on. I have been told that reducers such as those by Meade won't work because they will try to correct problems that don't exist in the Tal. The only option I can see is to use the 2" reducer made for the Tal250K. After speaking to the manufacturer, this reducer should do a fairly good job at correcting field aberrations. I had plans to get one but the price is approximately $400 and is out of my price range. The Intes Mikro reducer may also work because it's designed for flat-field systems. You can certainly try to image at native focal length.

I believe that the Tal has the potential to be a great imaging scope. You only have to look at some of Bert's (avandonk) images taken a few years ago using his Tal200K and a full-frame dslr to see what can be achieved.

If imaging isn't your thing, then this scope is great for visual purposes.

Reason for selling: A 6 week old and 2 year old means I don't have much time to image these days. When I do get a chance to image, I'm happy using my 8" Newt.

What you get:
1) Tal200K OTA
2) Original 1.25" R&P focuser
3) New back plate with SCT thread
4) Extra low profile 2" Crawmach focuser
5) Tal diagonal
6) 8x50 finderscope

Price: You can get a new OTA from Matthew Lovell (in Adelaide) for $1,820. The Crawmach focuser cost me $170 and the new backplate was $50.

I'll sell the lot for $800 + postage (I would prefer local pickup but can organise postage via courier. I have no idea how much this would be at this stage. I do still have the box that I brought the scope home from the US. It's filled with foam)

Pics of scope tomorrow. PM me if you have any questions.

[swannies1983 (Dan)]

Pictures added


Pic 1: Tal OTA with extra low profile 2" crawmach focuser
Pic 2: Top of OTA.
Pic 3: Showing primary
Pic 4: Custom made back plate with SCT thread
Pic 5: Original 1.25" focuser with Tal diagonal.

[swannies1983 (Dan)]

I will also consider selling OTA in original form i.e. I'll attach the 1.25" focuser and sell the Crawmach separately. However, I won't sell the Crawmach until the Tal is sold though.

[Poita (Peter)]

Do you get spikes in the images or does the curved vanes minimise that?

[swannies1983 (Dan)]

Yes Peter, the curved vanes do minimise spikes. You can see this in my image but also look at Nenad's review that I provided a link to. About halfway down there's a bit discussing this with an image of a bright star showing very little in the way of diffraction spikes:

TAL 200K seems to be unique with its curved spider vanes that were supposed to reduce diffraction spikes around bright stars. The concept is obviously working, leaving only minor spikes around the star that originate from sharp corners where vanes meet the secondary holder and the aperture opening.

[swannies1983 (Dan)]

I know of one other person who has updated their 1.25" focuser to a 2" one on their Tal200K and has imaged using the Tal250K focal reducer. His name is Evgeniy and goes by the name passer_by on the Russian Tal forum http://npzoptics.ru/forums/ (use google translator).

Have a look at one of his pictures that he took with a modified Tal200K + Tal250K focal reducer. Pretty impressive

NGC7635+M52, TAL 200K+ focus reducer, QHY8, 14 Images for 20 minutes

http://img-novosib.fotki.yandex.ru/get/5312/100245359.0/0_6b373_c6decbe_orig

[swannies1983 (Dan)]

Also, I forgot to add that the 8x50 finderscope is also included. It does appear to have a few blemishes around the edges of the glass but they don't appear to cause any issues. I can post images upon request.

[swannies1983 (Dan)]

Due to unfortunate circumstances with the previous buyer, this scope is now back up for sale.

[swannies1983 (Dan)]

Here are a couple of other pictures taken by Evgeniy with his modified Tal200K + Tal250K focal reducer

M13, TAL 200K+ focus reducer, QHY8, 12 Images for 200 seconds
http://img-novosib.fotki.yandex.ru/get/4523/100245359.0/0_6b370_a8a5529c_orig


NGC7023, TAL 200K+ focus reducer, QHY8, 24 Images for 10 minutes
http://img-novosib.fotki.yandex.ru/get/5821/100245359.0/0_6b372_61875fa_orig

[brian nordstrom (As avatar)]

Woaw Dan those photos go so deep , awsome .
Brian.

[swannies1983 (Dan)]

Thanks Brian. I wish I could say they were my pics. I just don't have the time to get my setup to the same point. Mind you, only the focal reducer is required. I've done all the hard work . They certainly show what these scopes can achieve.

These scopes also hold collimation very well. In fact, given their design, you shouldn't have to worry about collimation at all. Plus, the open design helps to reduce cool down time.

I fear there might be some reluctance to buy as there aren't a lot of these in Australia. They are more popular in Europe. Second hand ones are very difficult to come by because owners know how good they are.

[brian nordstrom (As avatar)]

Thanks for you honesty there Dan , have you googled " Astronomy Forums " ? yet this is an english version of IIS , and they speak highly of these Tal scopes .
Brian.

[swannies1983 (Dan)]

Yep, I have visited that site. Another one is Stargazers Lounge. There used to be a social group on that site but all groups were closed when the admin changed over servers. There's also a Tal Yahoo Group, which has been active since about 2002.

[swannies1983 (Dan)]

Here's a link to a website showing some Jupiter, Mars and Saturn images taken using a Tal 200K. The imager (Jon) goes by the name Rawhead on Stargazer's Lounge.

[swannies1983 (Dan)]

Price drop. Now $900 plus postage Less than half price of a new one and it's been modified with a 2" focuser. It's got to go!

[swannies1983 (Dan)]

Final price drop....$800.

[swannies1983 (Dan)]

Ok I'm willing to split this setup if it helps.

Tal200K with original 1.25" focuser and Tal diagonal - $650 + postage

This is still a great setup for visual use and planetary imaging.

Extra low profile 2" Crawmach focuser (basically brand new) - $150 + postage *SOLD*

I would prefer not to sell the focuser until the Tal sells.

[swannies1983 (Dan)]

Focuser now sold. Tal OTA still up for sale.

[swannies1983 (Dan)]

While the 2" Crawmach focuser is now sold, I will throw in the adapter plate (used when upgrading the 1.25" focuser to a 2" focuser) for FREE (I paid $50 for it).

[Regulus (Trevor)]

Can't believe this is taking so long to sell.
The links to photos you have are pretty damned good.
I remember when I sold 0ptics and specialist photographic equipment that the stuff these guys made was very good and made to withstand small nuclear bombs.
The Russians seemed to have one design philosophy and it was make it as good a quality as we can and don't worry to much about the cosmetic appearance, after all we aren't American sissys. Then make it to do a hard days work very well. After all the same product they sold to citizens and the west were used by their military, scientists and schools and they seem to have carried some of this philosophy into the present. And they are very clever at design.
My 1953 Werra III camera system is amazing and the 100mm Zeiss lens is still considered one of the sharpest lenses ever made. The difference between the consumer and military model? The mils had army green leatherette and the consumer/west got black. As good as a rangefinder Leica IMHO. Interchangeable lenses (35/50/100), Range-finder focusing with light-meter and Aperture/speed readout in the viewfinder and film advance by twisting the lens mount a half turn (so every adjustment was done with the one hand in the one position) and bomb-proof. Oh, and once you set an aperture-speed combo they locked together so you could change for depth of field or speed and the other variable changed automatically. Amazing design.
The Chinese got onto this in the late 90's and started shipping incredible optics cheap to get western money for the economy.
So the TAL is probably a bit heavy but the optics and mechanisms should be sound and if not it will probably tolerate serious tinkering better than some other name brands.
Good luck.
http://www.telescopes.ru/ and reviewed here and a dozen other places
http://www.cloudynights.com/item.php?item_id=832
http://www.cloudynights.com/item.php?item_id=713

Trevor