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Pimping your 102mm gt OTA.. Like what?

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#1 spongebob@55

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Posted 25 March 2013 - 01:53 PM

Like most of your I guess we like messin' with $59 OTAs, especially when the skies haven't been clear for what seems like months. Many of us bought the 'special' deal 102mm f/9.8
from OPT. What are you doing to yours to 'improve' it?
I'll start.

1. Remove with Synta Grease and replace with Pete's Red grease. I used Naptha. Is there anything better?

2. Remove short dovetail. Surprise, paint wasn't cured and two lines appear in finish from pressure of dovetail.

3. Insert 1/8" black hole plugs into dovetail holes. (plugs are on their way; not here yet.)

4. Replace metal focuser ring screws with black nylon ones so as to not mar accessories. M4's if I remember correctly.

5. Install flocking on dew shield.

6. Buy black 'foamies' from Jo-annes and make a longer dew shield.

7. Use a red dot finder b/c if I can't see it in that, its not going to be useful since I'm in a whiter than white zone. My light pollution laughs at your light pollution!

8. Rings and a long dovetail. Have to balance this thing!

9. Find some big honkin' jars/cans with plastic lids to fit and make aperature masks to test CA/detail reduction vs. apo or fringe filters on bright objects.

I think that someone somewhere here bought teflon and replaced the focuser gliders, but can't remember that...a little help here. Perhaps on a ST80 thread...

I would love a new focuser, but I don't think it would improve any visual qualities? Or?

Can you take the objective out of its cell and are the edges blackened?

Regards,
Bob

#2 PatHolland

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Posted 25 March 2013 - 02:34 PM

Bob, do you know what rings to get that clamp on (rather than delrin tips?) I think I will make that mod if I can.

#3 spongebob@55

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Posted 25 March 2013 - 02:43 PM

Hey Pay, I bought the 4" from Scopestuff. http://www.scopestuff.com/ss_rings.htm I haven't gotten them yet, but I measured the OD of the OTA so I'm pretty sure that's right.

#4 buddyjesus

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Posted 25 March 2013 - 03:34 PM

I had a bit of a head start on doing a kaizen treatment to my 102hd, but for all intents and purposes it is the same scope made by synta.

1. I cleaned out the grease and replaced with a light amount of white lithium lube.

2. I had to rotate the lenses to remove astigmatism. Took days but worth it.

3. Using a collimating laser, I had to do some butchery to the tube to make the focuser aligned with the optic. I made the screw holes(which had some rather sizable slop) into slots and this actually firmed up the focuser.

4. I had to dump the 6x30 finder and made my own rings and 7x50 finder out of a junk bino. This is going to be replaced soon with a used but proper 9x50 straight through finderscope. These are much cheaper than the RACI alternatives.

5. I added a classic tasco motorfocuser.

6. I chose to paint the inside of my dew shield flat black, but think felt will be coming to incrementally improve upon that eventually.

7. Made a long posterboard tube for use as a dew shield when in the city. This just slides inside the existing dew shield.

8. there is a bit of slop in the lens cell where it is screwed into the body. I pushed it down onto the tube all the way so I have that position as a reference in case the end of the tube gets bumped. I used a SMALL amount of wood filler inside the screw holes to firm it up. If it is messy, you are doing it wrong.

9. I lost my end cap for the objective, so I added a bit of electrical tape to the circumference of the dew shield so I would get a snug fit using the lid of an oatmeal box. I also used spares of this to make different sizes of aperture masks to recreate historic observations. My favorite is the 15mm mask for Galileo's observations.

10. Several more mods for the CG4 it sits on.

#5 buddyjesus

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Posted 25 March 2013 - 03:38 PM

I am looking to also see about having a second tension screw added to the focuser by a buddy of mine that does machining. This will limit the tipping of the focuser draw tube I recon.

#6 spongebob@55

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Posted 25 March 2013 - 03:48 PM

I am looking to also see about having a second tension screw added to the focuser by a buddy of mine that does machining. This will limit the tipping of the focuser draw tube I recon.


Hello Buddyjesus,
Do you recall if the objective lenses were blackened when you rotated them?
Some good ideas. I hope that someday the skies will clear and I can observe instead of spending too much time on these boards.

#7 buddyjesus

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Posted 25 March 2013 - 05:21 PM

no they werent. good idea, but would make aligning the lenses afterwards a bit tough possibly. What would you recommend blackening em with?

#8 audioaficionado

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Posted 26 March 2013 - 03:47 AM

I think that someone somewhere here bought teflon and replaced the focuser gliders, but can't remember that...a little help here. Perhaps on a ST80 thread...

Regards,
Bob


Reworking a Synta Focuser

#9 Widespread

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Posted 26 March 2013 - 08:53 AM

I opened the box, peeled off the protective material, and attached the OTA to my Porta II on a wooden tripod. That's it. :cool:

Of course, I may do more after first light, but for now it's just sitting there, dwarfing my SVR90T on its SLT tripod/mount.

no they werent. good idea, but would make aligning the lenses afterwards a bit tough possibly. What would you recommend blackening em with?


The videos I've seen on modifying the ST80 recommended a black felt Magic Marker. I've always been too worried that I wouldn't be able to put things back together properly (in my case, a real risk, unfortunately), but if you can hacksaw your OTA, I'm sure you won't have that problem.

#10 t.r.

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Posted 26 March 2013 - 08:57 AM

"Buy black 'foamies' from Jo-annes and make a longer dew shield"

What exactly are these? Good for dewshields eh?

#11 spongebob@55

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Posted 26 March 2013 - 02:27 PM

"Buy black 'foamies' from Jo-annes and make a longer dew shield"

What exactly are these? Good for dewshields eh?


They are 2 or 3mm thick foam sheets that come in all colors, black being the one of choice. I buy the 3mm ones and have made dew sheilds for my CPC1100, my C14 and now my 102GT by gluing them together and then velcroing a strip. I just wrap it around the scope, join the velcro and it stays on the end of the OTA. The foamies aren't super stiff, but they're stiff enough to hold a round shape. Especially true on a 102mm scope. You can also roll it up for easy storage. They cost about 1-2 bucks each, depending on the thickness and if you have a coupon from JoAnnes' :D
You can also use them to line storage boxes or shapes that touch your telescope so as to not scratch the OTA, etc.
bob

#12 spongebob@55

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Posted 26 March 2013 - 03:15 PM

I think that someone somewhere here bought teflon and replaced the focuser gliders, but can't remember that...a little help here. Perhaps on a ST80 thread...

Regards,
Bob


Reworking a Synta Focuser


thanks Steve.......

#13 avarakin

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Posted 28 March 2013 - 08:10 PM

2. I had to rotate the lenses to remove astigmatism. Took days but worth it.

Could you tell us how you did this?
It looks my scope has some astigmatism.

Alex

#14 buddyjesus

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Posted 29 March 2013 - 01:26 AM

some say that if you have a digital micrometer, you can line up the thinnest part of one of the lenses with the thicker part of the other. I didn't have one and went the old fashioned way.

I kept the flint stationary inside the tube while gently loosening the screw on part of the plastic cell. This really sticks the first time you loosen it so be prepared for the lenses to jump out at you. The lenses should not be have this tightened down so hard anyways as it will pinch the outside of the optic. Afterwards I tilt the tube down to let just the crown pop out. I wear rubber gloves to cut down on fingerprints. I marked the crown with a perminent marker for reference(12 o'clock position.) Then since you have astigmatism at your current spot, rotate about one hour on the clock face. Then you retest. Repeat, retest, repeat retest, etc. When you find your sweet spot, which might take a while, you keep it there. Next time you remove both lenses for cleaning, you want to mark the flint where it lines up with the line on the crown.

I hope this makes sense. If not I am around the boards a lot.

#15 audioaficionado

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Posted 29 March 2013 - 04:09 AM

some say that if you have a digital micrometer, you can line up the thinnest part of one of the lenses with the thicker part of the other. I didn't have one and went the old fashioned way.

I kept the flint stationary inside the tube while gently loosening the screw on part of the plastic cell. This really sticks the first time you loosen it so be prepared for the lenses to jump out at you. The lenses should not be have this tightened down so hard anyways as it will pinch the outside of the optic. Afterwards I tilt the tube down to let just the crown pop out. I wear rubber gloves to cut down on fingerprints. I marked the crown with a perminent marker for reference(12 o'clock position.) Then since you have astigmatism at your current spot, rotate about one hour on the clock face. Then you retest. Repeat, retest, repeat retest, etc. When you find your sweet spot, which might take a while, you keep it there. Next time you remove both lenses for cleaning, you want to mark the flint where it lines up with the line on the crown.

I hope this makes sense. If not I am around the boards a lot.


I have the exact same scope and mount you do. I'm thinking the person who previously owned my scope took it apart and messed things up quite a bit.

#16 spongebob@55

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Posted 29 March 2013 - 10:45 AM

Here's a picture of the 'foamie' dew shield. The plastic dew shield opens up a bit the more forward it goes, so this is a good way to do it since the foamie stretches a little.

Attached Files



#17 spongebob@55

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Posted 29 March 2013 - 10:47 AM

and here's a picture of the 1/8" plastic hole plugs plugging the dovetail bolt holes.

Attached Files



#18 rtomw77

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Posted 30 March 2013 - 08:25 AM

The only things I plan to do are:

Make a longer light shield with either cardboard/flat black paint/duct tape or black foam as described above.

Attach a Rigel RDF. Rubber bands will do until I find the best spot for it.

Add some weight to the front of the tube so I can use the 2" diagonal and EP's. I have a spare Telrad base and might use rubber bands to put my Telrad at the front of the tube for now, and wait until later to mount the Rigel RDF.

Eventually get some 4" rings when I have some spare cash. Removing the short dovetail bar and using 1/8" plugs on the existing screw holes is a nice touch.

The New Scope Curse has prevented first light so far so I have plenty of spare time to play around.

Tom

#19 spongebob@55

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Posted 30 March 2013 - 09:17 AM

The only things I plan to do are:

Make a longer light shield with either cardboard/flat black paint/duct tape or black foam as described above.

Attach a Rigel RDF. Rubber bands will do until I find the best spot for it.

Add some weight to the front of the tube so I can use the 2" diagonal and EP's. I have a spare Telrad base and might use rubber bands to put my Telrad at the front of the tube for now, and wait until later to mount the Rigel RDF.

Eventually get some 4" rings when I have some spare cash. Removing the short dovetail bar and using 1/8" plugs on the existing screw holes is a nice touch.

The New Scope Curse has prevented first light so far so I have plenty of spare time to play around.

Tom


Hi Tom, some good ideas there. I like the Rigel. I have a red dot finder, but its still a little close to the OTA.
With 2" accessories, it is SOOOO back heavy, I had to use ankle / wrist weights attached to the front (and taped) to get it to balance.
Also, when I used flocking material for the dew shield, I realized that the inside of the plastic dew shield is shiny so a good roughing up and flat black paint is a very good thing to do.
Good luck with the scope and weather! We FINALLY look like we have a good, long night to observe tonight in the NE.
Clear skies
Bob

#20 rtomw77

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Posted 30 March 2013 - 12:06 PM

SB@55

I put the OTA on my Vixen Porta II on the Hal-130 tripod (aka Star Guy) and played around with combinations of various accessories.

The balance with the included dovetail was fine with a 6X30 finder, a 1.25" diagonal, and a typical 1.25" EP.

Using rubber bands to mount a Telrad up front did improve the balance some with the 2" items. A dew shield extension should help some more.

How much extra length did you make your dew shield extension? It looks to be around 6" extra.

Thanks,

Tom

#21 spongebob@55

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Posted 30 March 2013 - 03:47 PM

Hi Tom, the 'foamie' dew shield is 10" long, but once you put it on and adjust it, it can be up to 8" long. Remember the plastic dew shield is not a perfect cylinder, it flares larger so if you make one, consider that issue. Thats why I like the foamies; they stretch.
Regards,
bob

#22 buddyjesus

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Posted 30 March 2013 - 10:14 PM

I use a finderscope mounted up near the top of the scope because it is more ergonomic. It can be tough to look through straight through finders mounted at the bottom of the scope.

I chose to pain flat black on the inside of the dew shield with improved but lacking improvement. Sort of moot since I made the posterboard shield, but want flexibility for different situations.

#23 rtomw77

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Posted 31 March 2013 - 07:10 AM

Had first light this AM using the OTA on a Porta II/HAL-130 on VSP using a 1.25" diagonal and EP.

The scope gives pleasant views with some color as expected.

The short dovetail bar is enough to balance things as long as you use lightweight 1.25" EP such as standard Plossls. Heavier 1.25" EP need extra weight added to the front of the OTA.

A set of 4" tube rings and a longer dovetail bar have become priority items for me.

Tom

#24 spongebob@55

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Posted 20 August 2013 - 08:35 PM

Like most of your I guess we like messin' with $59 OTAs, especially when the skies haven't been clear for what seems like months. Many of us bought the 'special' deal 102mm f/9.8
from OPT. What are you doing to yours to 'improve' it?
I'll start.

1. Remove with Synta Grease and replace with Pete's Red grease. I used Naptha. Is there anything better?

2. Remove short dovetail. Surprise, paint wasn't cured and two lines appear in finish from pressure of dovetail.

3. Insert 1/8" black hole plugs into dovetail holes. (plugs are on their way; not here yet.)

4. Replace metal focuser ring screws with black nylon ones so as to not mar accessories. M4's if I remember correctly.

5. Install flocking on dew shield.

6. Buy black 'foamies' from Jo-annes and make a longer dew shield.

7. Use a red dot finder b/c if I can't see it in that, its not going to be useful since I'm in a whiter than white zone. My light pollution laughs at your light pollution!

8. Rings and a long dovetail. Have to balance this thing!

9. Find some big honkin' jars/cans with plastic lids to fit and make aperature masks to test CA/detail reduction vs. apo or fringe filters on bright objects.

I think that someone somewhere here bought teflon and replaced the focuser gliders, but can't remember that...a little help here. Perhaps on a ST80 thread...

I would love a new focuser, but I don't think it would improve any visual qualities? Or?

Can you take the objective out of its cell and are the edges blackened?

Regards,
Bob



With all the additional OTAs that have been purchased with this second round of $59 + shipping pricing, I thought I'd renew this thread.
I actually sold my original 102mm but have missed it so much, I just bought another, and it should be here on Friday.
Thanks to another poster, Jarrod, I also bought the AR102 ring assembly from Explore Scientific today. Much superior rings/dovetail/handle than what I had before. I now have to make my foamie dew shield and the other things above....
Bob

#25 dpippel

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Posted 21 August 2013 - 09:35 AM

and here's a picture of the 1/8" plastic hole plugs plugging the dovetail bolt holes.


Bob, thanks for reviving the thread. Where did you get your plastic plugs?






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