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Pentax Telescopes & Mounts

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#151 Steve_M_M

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Posted 11 September 2021 - 10:31 PM

My new to me ZWO ASI183MC camera has arrived.  My first camera since imaging with an Olympus Om1 film camera in the 1990’s.  The ASI AIr Pro and camera connected easily and I was up and running in 15 minutes.  
 

I have no idea what I am doing or what settings to use on the camera, but these are the first few images tonight with the Pentax 75EDHF.   Obviously no processing as I haven’t a clue about that. 
 

These are 10 second images from Austin,Tx(about mag 2 skies). I was amazed to see the central star in M57 with the little Pentax. 

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Edited by Steve_M_M, 11 September 2021 - 10:32 PM.

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#152 Defenderslideguitar

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Posted 12 September 2021 - 05:12 PM

I have the Pentax 75 edhf

when I got it I needed help and adapters to get it to focus at all....back focus issues

Once I got the right custom adapter   thanks Steve    I had not really used it   now  the optics are really good but  I recently noticed the focuser rod has the slightest bend to it   it is also missing one of the four focuser screws on the far right....

 

I wonder where I might go for assistance   then I wondered it a moonlite focuser could be installed?  I have learned what most of you already knew about the Pentax-centric focuser adapter line up

 

any ideas? 

thanks



#153 RichA

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Posted 12 September 2021 - 05:15 PM

I have the Pentax 75 edhf

when I got it I needed help and adapters to get it to focus at all....back focus issues

Once I got the right custom adapter   thanks Steve    I had not really used it   now  the optics are really good but  I recently noticed the focuser rod has the slightest bend to it   it is also missing one of the four focuser screws on the far right....

 

I wonder where I might go for assistance   then I wondered it a moonlite focuser could be installed?  I have learned what most of you already knew about the Pentax-centric focuser adapter line up

 

any ideas? 

thanks

Replacing a screw is easy, you may be able to coax (carefully) the pinion back into straight shape on a vice, but it's a risk.  Moonlight makes a lot of adapters for their focusers so measuring the diameter (I.D.) of the tube and asking them if they have an adapter would be good.  You can drill new holes in the adapter to match your OTA.


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#154 Defenderslideguitar

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Posted 12 September 2021 - 05:19 PM

Thanks Rich

 This is the type of info I need     I will contact them



#155 GilATM

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Posted 14 September 2021 - 04:28 PM

Looking for help in identifying this beautiful little mount.   I can not find any identification other than "Pentax".

 

I bought this little mount years ago and am just now getting around to examine it.    The tripod is about 40" high at it's greatest height.  The polar axis is 20mm in diameter.  It has a polar axis scope.  It has silky smooth gearing with little to no backlash.   The knobs are all plastic.   The holes for the eyepieces are only 25mm in diameter.  

 

I would most like to motorize it so that I might do some guided astrophography with it and a small scope. 

 

Gil

 

 

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#156 coinboy1

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Posted 14 September 2021 - 05:31 PM

Thats a Pentax MS-2 mount
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#157 GilATM

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Posted 14 September 2021 - 06:13 PM

Thanks! Has anyone adapted one to a drive, either just for autoguide or for goto (such as onstep)?

#158 GilATM

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Posted 15 September 2021 - 01:42 AM

Looks like someone did convert the MS-2 mount for astrophotography - but it looks like it may not worth the trouble.   I can only read using the automatic Google translation from Japanese - so I don't know how accurate it is.   It mentions that the Dec is "only a spring and a gear" and would need to be rebuilt for full rotation.

 

http://oldphoton.blo.../pentax-75.html

 

 


Edited by GilATM, 15 September 2021 - 01:47 AM.

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#159 gwfbmd

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Posted 15 September 2021 - 04:24 PM

I do not like the declination design on these mounts and I would not put any extra time into such a mount.  A spring and a gear is an apt description - and it is frustrating to have the clamps locked down and still have it movable against the spring!

 

My Pentax mount worked much better when I was using .965 eyepieces.  I am now using big 2" MWA and UWA eyepieces, and the mount is no longer up to the task.  The counterweight is too small, the tube won't slide enough in the saddle to balance, and the aforementioned declination axis is a joke.

 

I will probably take the saddle off and stick it on a rail for my LX85.  Now, that will be awesome.  The Pentax mount will inherit a PST, if I ever have time to fool with it.

 

By the way, I was observing The Helix and The Veil at a dark sky with the 75EDHF last week.  It was all so great.  Also, numerous experienced observers pronounced that the view of Saturn was without a doubt the best any 75mm telescope in the world could possibly provide.  We also observed the GRS on Jupiter and a transit of Io.  I could easily see the structure of the clouds where they lead into the GRS.


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#160 GilATM

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Posted 15 September 2021 - 11:18 PM

I do not like the declination design on these mounts and I would not put any extra time into such a mount.  A spring and a gear is an apt description - and it is frustrating to have the clamps locked down and still have it movable against the spring!  ....

That is unfortunate.   I too had thought of using it for my little PST - the size seem just right, but even then I would like to have a simple RA drive.   It could then double as a wide field mount for unguided astrophotography - but if the DEC is not reliably still, then that utility is lost as well.  

 

Gil


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#161 Defenderslideguitar

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Posted 16 September 2021 - 11:24 AM

I too have the venerable Pentax 75 edhf     the optics are so good and surprisingly  I was very pleased with how it did on planets considering its design         with the built in reducer it does some wide stuff very well and if I ever get my Cannon t2i on it I may learn more of what it is designed to do....

 

Now   not to be contrary with the Pentax 75  but   for planetary in this size range    I'll take the 1992  Tak FC 76   against all comers 

it is simply special in my view   


Edited by Defenderslideguitar, 16 September 2021 - 11:24 AM.

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#162 Haukka

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Posted 23 September 2021 - 01:14 PM

Hello there,

 

by chance, does anybody knows what is the thread size on the 75 SDHF (see arrow) ? I'd like to directly connect a full-frame CCD on it. Thanks in advance smile.gif

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#163 AnakChan

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Posted 09 January 2022 - 12:22 AM

Thought I'd use this opportunity to show off a custom AutoFocus solution for my Pentax 125SDP by Joshua Bunn who's based in Albany, Western Australia. As many of you who have Pentax with helical focusers (or Vixen VSD100, etc.) may know, finding an AF solution is a PITA despite the focuser itself actually being really sturdy and solid for a heavy camera payload.

I passed my scope and an EAF to Joshua last year for him to come up with some fancy way to automate AF and he came up with the following - a bracket to hold the EAF, and a custom design tightening ring sprocket with pitch-size to match the belt. I've seen other solutions that slip a belt straight onto the existing Pentax/Vixen rubber focus grip but that could be prone to slippage. And I've also seen an old pix with a (robofocus?) motor with a custom ring however couldn't figure out who made that. So Joshua made a custom ring that replaces the Pentax rubber focusing grip.

IMG_9009.jpeg IMG_9029.jpeg IMG_9030.jpeg

This setup has worked beautifully. Autofocusing via N.I.N.A. was perfect straight out of installation :-

270132102_615343076393273_8998659396588417182_n.jpeg

I can slip the original rubber focus grip back on if I want to restore back to normal.


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#164 deSitter

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Posted 09 January 2022 - 07:55 AM

I have the Pentax 75 edhf

when I got it I needed help and adapters to get it to focus at all....back focus issues

Once I got the right custom adapter   thanks Steve    I had not really used it   now  the optics are really good but  I recently noticed the focuser rod has the slightest bend to it   it is also missing one of the four focuser screws on the far right....

 

I wonder where I might go for assistance   then I wondered it a moonlite focuser could be installed?  I have learned what most of you already knew about the Pentax-centric focuser adapter line up

 

any ideas? 

thanks

Here is how to deal with a bent pinion.

 

Get two boards, about 1' x 6" x 1/2" - at about 10" up the board, drill a hole so that the end of the pinion fits into it very snugly. It should be tight enough that you have to work the pinion to and fro to coax it out of the hole.

 

Now very carefully push the boards together against the bend, in tiny increments so you don't overshoot. The boards give you enormous leverage and it is very easy to unbend the pinion if it is not already mangled. Note that brass will succumb to metal fatigue quickly, so you don't want to overshoot and have to bend the other way. You might mark the bend with a sharpie - roll it back and forth on two books with the gear in the gap between them.

 

-drl


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#165 Defenderslideguitar

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Posted 09 January 2022 - 12:28 PM

R

Thanks so much for the suggestion

I will give it a  go      very slowly 

thanks

B



#166 photoracer18

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Posted 10 January 2022 - 06:33 PM

I am ready to do a comparison with my 75EDHF, the Pentax 85, and an Orion Eon 115mm.  They are all mounted and aligned on my G11 and ready to go.  Unfortunately, the weather forecast has us all locked down with clouds for at least the next 10 days.

 

By the way, I see a 75SDHF just sold with finder and clamshell for $1100.  Is there a huge difference between the EDHF and SDHF?  I know the differences in the build, but is the SDHF noticeably better at the eyepiece?

Pretty sure the SD has lower dispersion glass than the ED.



#167 ccwemyss

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Posted 15 January 2022 - 03:03 PM

I just adapted a Celestron Logic Drive to my Pentax 85 mount.

 

Pentax Drive - 1.jpeg

 

It turned out to be quite easy. I bored out the mount end of the flexible coupling to 21/64" (closest I could come to the metric size), with an 11mm depth, and the CG-2 bracket is almost a perfect fit -- needing just a bit of filing to extend the slot by about 1mm. A 6mm screw secured it to the hole in the left side of the mount. On that side, it turns the mount the correct direction when set for the northern hemisphere. The bracket positions the drive at a perfect distance. It has plenty of torque to turn the mount, just using its internal 9V battery. 

 

Pentax Drive - 2.jpeg

 

I'm hoping the drive, which has a fairly wide range of speeds, will be adjustable to provide good visual tracking. This isn't going to serve for photography - the logic drive uses an oscillator that's controlled by a potentiometer, so it will vary with temperature. But it will be great just to be able to keep objects in view for a few minutes at a time. 

 

The 85 didn't include a drive as standard, like the 100, and very few people paid for the option, so the vintage Pentax drives are hard to find. They also need a 12V power source. This one is self-contained. It does interfere with the tube at some angles near zenith, but I don't think it's much more than the Pentax would, because its depth is basically the same as a synchronous motor. 

 

Chip W. 

 

p.s. I got it out to test tonight, and with just a little adjusting of the speed control, the tracking was excellent. Things were staying where I put them for up to 10 minutes. With temperatures around 7*F, I wasn't going to spend a lot of time looking. But it was nice to be able to gaze at the trap and the moon using a 6mm Ortho (167X) for extended periods without having to turn the slow motion knob. 


Edited by ccwemyss, 15 January 2022 - 09:27 PM.

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