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04-11-2008, 09:48 PM   #1
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K10D on a telescope

Hi All!

Recently another thread here got me a little enthused about having a go at shooting the moon and stars, so for the recent pentax day i went to a surrounding town that has several observatories. There was no moon that night, but i got a few star shots with some success. The guy offered to let me put my K10D on one of his telescopes, but he didn't have a Pentax K mount adaptor. Pity, but if i can get the correct adaptor i can go back easily enough.

I'm under the impression the telescope needs a 'T-mount' adaptor. looking at one it looks remarkabily similar to a M42 one, but i don't have any screw mount lenses to try it. anyone know what the difference is?

I'm, after some information so i can make the most of the return trip.

The telecsope is, AFAIK, essentially a big prime lens. variable focus, but fixed zoom.
What about aperture? this would also be fixed wouldn't it?
Any suggestions on how to set up my K10D to work in this setup would be appreciated.

(sorry, i don't know what telescope it was. a 14inch something or other )

Thanks

Mark

04-11-2008, 09:58 PM   #2
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The thread spacing of a T Mount is slighty different to that of a M42 Mount though the diameter is still the same.
04-12-2008, 03:29 AM   #3
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You need a "T mount to Pentax K" adapter.
(Of course, not "Pentax Threaded" as this is just a synonym for M42 )

Go to your favorite astro shop online or locally (expect to pay about 20$).

Even with the adapter, there may be issues with the distance of the focus plane. But if other SLRs have already been mounted ok, no problem.

You may also find it hard to impossible to focus properly. A K20D with magnified LiveView, a "Scheiner mask" in the scope, or a 14x magnification loupe (used instead of the camera while focussing) would help. Ideally, people at this place should be able to help you with this.
04-12-2008, 06:12 AM   #4
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T mounts are carried at any decent camera shop. The threads are different than Pentax screw. There actually are T mounts with Pentax screw on opposite end. Make sure you get Pentax K T mount. Enjoy. This could get to an expensive new hobby.
thanks
barondla
14" scope is a real nice size.

04-12-2008, 06:49 AM   #5
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A word of warning - I bought a Celestron T Ring for my K10D. I checked that if fitted my 5 inch reflector telescope then went on a 3 week holiday to the Pyranees armed with telescope and camera hoping for some great shots in pitch black nights without any light pollution.

Got set up, finally tried to mount camera. The T-ring, although it says Pentax K/M and looks very similar to Pentax K/M mounts, did not fit my camera. It was too big.

The dissapointment was bitter. I should have checked averything before I left, but I failed to check the most basic thing. https://www.pentaxforums.com/forums/images/smilies/green.gif

My son subsequently bought me for Christmas some astrophotography kit including the T-ring from another supplier. Guess what? It was EXACTLY the same as the one I had bought previously and did not fit.

I am now recluctant to order another one - so if you can find a supplier that has a genuine T-ring for for the Pentax --- Please let me know.
04-12-2008, 08:15 AM   #6
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QuoteOriginally posted by ukbluetooth Quote
I am now recluctant to order another one - so if you can find a supplier that has a genuine T-ring for for the Pentax --- Please let me know.
Strange.

I knew my T-mount adapter fits my *istDS and just checked with my K20D: ok.

It is "hama Camera-Adapter Pentax-K" #30701
hama.de | 00030701 HamaKamera-Adapter T2 für Pentax K-Bajonett

Hama is German though, I think Meade makes another adapter.
04-12-2008, 02:13 PM   #7
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they should be all the same as the cameras are all the same else how can all lenses made in the last 30 years fit ?
04-12-2008, 05:17 PM   #8
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You should check celestron.

I have a C90 spotting scope, bought it in the early 1990's with T0mount.
works just fine

04-12-2008, 07:15 PM   #9
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I have 4-5 different T-mounts for Pentax K - all fit my ist DS just fine. One problem I ran into though, involved the telescope adapter/PK mount I bought.

When I first tried it, it didn't fit. As I looked closely at it, I realized it didn't have the red dot. I just kept trying it (carefully!!), rotating it one tab at time, until it fit. Once I figured out where to mark it, I put a small dab of my wife's mail polish on it and created my own "red dot".

Check yours and make sure you haven't fallen into the same trap I almost did.
04-12-2008, 08:48 PM   #10
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Hi Bob,

I use my Televue-76 with my K10D and my K100D.

Televue makes a 2 inch tube -> T-ring that I use with my scope. (they just call it a camera adapter)
Here's a thread I started a while ago that shows what I've done with my telescope and a Pentax.
https://www.pentaxforums.com/forums/post-your-photos/18801-long-slow-glass-birds.html

T-ring and M42 are different, from what I've heard (I don't have anything M42), so make sure you're not using one on the other. I'm not sure if the threads on one will chew up the other, but I wouldn't expect it to thread properly, either... If it doesn't go "smooth as silk", don't force it!

-Chris

-Chris
04-13-2008, 06:50 AM   #11
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Hi!

I went into my local camera store and found a T mount adaptor for AU$22 and the guy said i could bring it back if it didn't fit.

It fits my camera fine, but i think i'll have to post it to the guy and ask him to try it on his scope.

As far as the telescope side, he has used other cameras (he has a specalised one as well as a Canon 300D) so we should be able to figure the focus side out.

I've read that results are better (less noisy) if you keep the iso low and lengthen the exposure time.

As far as the camera settings, should i just set it to manual and treat it like an older lens? or is there an easier way?

Thanks

Mark
04-13-2008, 11:48 AM   #12
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Hi Bob,

Yes, I use manual when using my telescope, and the green button when I want to meter, which is relatively infrequently... I usually just trial and error until I'm close, then bracket. At 480mm, I find that shutter speed on a fixed mount shooting stars @ 480mm must be 2 seconds or under. Any longer and the stars start too look like lines, rather than points. (Stop the world I wanna get off! )

QuoteQuote:
I've read that results are better (less noisy) if you keep the iso low and lengthen the exposure time.
This really depends on what you're shooting. I'd definately keep the ISO low for moon shots, but for darker deep sky objects, high ISO is the only way I have enough light to pull out detail from something like the Orion nebula. In fact, I usually use my K100D (for ISO 3200), rather than my K10D for these darker objects. I don't get the kind of images you will find on the web, but rewarding none the less...

Here's a shot of Orion Nebula taken with my K100D, and my TV-76 @ f/6.3, 480mm, ISO 3200:



@ ISO 1600, it's really difficult to see any of the nebulous color (blues/reds/purples) around the center, even after heavy post process. But I'm going to start "stacking" soon, and see if I can't find more detail there. Lookup "astrophotography stacking" and you should find more details on how to approach it. I'm only getting started with this aspect myself, so don't have many pointers yet.

Good luck!

-Chris
04-13-2008, 04:06 PM   #13
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The difference between T-mount an M42 threads is, that M42 is a 42mm x 1.0 thread, whereas a T(2) mount is 42mm x 0.75 threaded.
If a T-mount is completely diffferent, it might be a T4-mount, which is old and rarely used anywhere (there were some third party lenses with this T4 mount in the long and distant past).

Al the telescope adapters I know off are T2-threaded (TeleVue, Pentax, Baader, Celestron and Meade) and fit standard T2 adapters easily.

Ben
04-14-2008, 04:34 AM   #14
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QuoteOriginally posted by ChipB Quote
I have 4-5 different T-mounts for Pentax K - all fit my ist DS just fine. One problem I ran into though, involved the telescope adapter/PK mount I bought.

When I first tried it, it didn't fit. As I looked closely at it, I realized it didn't have the red dot. I just kept trying it (carefully!!), rotating it one tab at time, until it fit. Once I figured out where to mark it, I put a small dab of my wife's mail polish on it and created my own "red dot".

Check yours and make sure you haven't fallen into the same trap I almost did.

Thanks - but they really are too big by several mm (about 9mm difference in diameter). They must have been made for an alternative camera (with a pentax looking mount) and been wrongly labelled at the factory. Obviously QC let some through. I know it seems strange.
04-14-2008, 05:10 AM   #15
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QuoteOriginally posted by ukbluetooth Quote
Thanks - but they really are too big by several mm (about 9mm difference in diameter). They must have been made for an alternative camera (with a pentax looking mount) and been wrongly labelled at the factory. Obviously QC let some through. I know it seems strange.

Pentax 645 mount ?
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