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Equipment Discussions >> Cats & Casses

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PowellAstro
scholastic sledgehammer
*****

Reged: 10/14/09

Loc: Tennessee
Re: C90 Contrast Issue new [Re: PowellAstro]
      #6264907 - 12/21/13 08:06 AM Attachment (26 downloads)

This second image shows the primary baffle attached to the collimation plate all as one piece. The brass colored shaft to the left is the focuser assembly and the largest part, at the top of this shaft is only 7/16 of an inch. This gives some scale for the baffle tube size. So, this had to of changed also.

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Sarkikos
Postmaster
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Reged: 12/18/07

Loc: Scotophobe Maryland, USA
Re: C90 Contrast Issue new [Re: PowellAstro]
      #6265021 - 12/21/13 09:54 AM

What is the entire length of the primary baffle? I didn't realize it was that long. Before I've only seen it in pictures where much of it was hidden by the primary mirror. Would the entire baffle from rear opening to inner opening need to be covered by the flocking? Or is not all of that tube attached to the backplate considered the "primary baffle?"

Mike


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PowellAstro
scholastic sledgehammer
*****

Reged: 10/14/09

Loc: Tennessee
Re: C90 Contrast Issue new [Re: Sarkikos]
      #6265037 - 12/21/13 10:03 AM

It is around 6 inches long and yes, I covered the whole length of the primary baffle.

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XyrcesFenol
member


Reged: 08/05/11

Re: C90 Contrast Issue new [Re: Karthik]
      #6275551 - 12/27/13 03:05 PM

Late question on the successful baffle mod with black sandpaper that you did, was the improvment also seen at night? I belive the initial contrast test was during daytime, and if it helps in the dark I will do it myself too.

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jrbarnett
Eyepiece Hooligan
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Reged: 02/28/06

Loc: Petaluma, CA
Re: C90 Contrast Issue new [Re: PowellAstro]
      #6275589 - 12/27/13 03:29 PM

During your project, did you get a sense of which portion of the sum total of the mod had the greatest impact? I'm wondering if putting sandpaper in the primary baffle yields >50% of your contrast improvement. It seems to be the simplest part of the project in that ut can be easily done by just about anyone without disassembling the telescope.

Regards,

Jim


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PowellAstro
scholastic sledgehammer
*****

Reged: 10/14/09

Loc: Tennessee
Re: C90 Contrast Issue new [Re: jrbarnett]
      #6275701 - 12/27/13 04:33 PM

The sandpaper in the primary baffle seems to be 80 percent of the total improvement! And yes, it can be done without disassembling the unit. If you only do one thing, that would be the one to do!

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Karthik
member
*****

Reged: 11/07/08

Loc: Erie, PA
Re: C90 Contrast Issue new [Re: PowellAstro]
      #6275774 - 12/27/13 05:18 PM

I agree, the sand paper in the primary baffle is all that i needed to see some improvement.

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doug mc
super member
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Reged: 03/21/09

Loc: Tamborine Mountain Australia
Re: C90 Contrast Issue new [Re: Karthik]
      #6275864 - 12/27/13 06:26 PM

If you look down the diagonal,eyepiece removed with your scope aimed outside at a daylit scene, you will see the the surfaces that need flocking. The internal baffle, although not the entire length, as the flocking also acts as a baffle, and sections of your diagonal will also require flocking. Daytime scene contrast is improved the most followed by lunar viewing. Flocking those areas in my 90mm mak and c6 improved contrast full stop.

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Asbytec
Guy in a furry hat
*****

Reged: 08/08/07

Loc: La Union, PI
Re: C90 Contrast Issue new [Re: XyrcesFenol]
      #6275947 - 12/27/13 07:03 PM

Quote:

...was the improvment also seen at night? ...if it helps in the dark I will do it myself too.



In my experience, the short answer is yes.

The long answer is it depends, in my experience which might differ from others. One night I removed the flocking and was shocked to see the FOV change in apparent brightness as I slewed the scope around the sky. There are some direct and indirect sources of lighting in the suburban setting, I believe some light was shining down the primary baffle depending on the angle and brightness of the source relative to the OTA. So, yes, there is a noticeable improvement and least in a suburban setting.

I suspect there is improvement on the moon, as well. Others have mentioned improvement near or while observing the moon. I don't know for sure, but certainly don't doubt their claims. In fact, there almost has to be some improvement. Really, point your scope at the moon and look up the visual back without the eyepiece. It's bright up there and the inner baffle wall, IIRC, is lit up, too. Now flock it and see how dark it gets, the opening is still bright but the inner wall is black, as I remember testing a couple years ago.

The fainter the object and the more oblique any direct light source is, the less the improvement is or might be. So, generally there is improvement at night, but it depends on how bright and where any direct (and maybe indirect) lighting is, IME. Flocking suppresses any light that can find it's way into the baffle from the upper end of the OTA. Remember, if you can look down your baffle - and you certainly can do that easily enough (bypassing the secondary baffle), light can get down there, too. If light can get in your primary baffle, it can find its way into the FOV. The amount of damage done depends on how bright the source is.

Another thing to consider is looking into the exit pupil of a low power eyepiece during the daytime. You may well see rings of brighter reflections surrounding the exit pupil. The trick is to find those sources of reflections and flock them, too. The closer they are to the exit pupil, the easier they can make their way into the FOV due to their small angle from the optical axis. And at higher powers (smaller exit pupils) those reflections can even follow the telescopic light directly into your own pupil and land on the retina just like an image of Jupiter does.


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ChristianG
sage


Reged: 10/18/12

Loc: Ottawa, Canada
C90 Contrast Issue--Protostar flocking board... new [Re: Asbytec]
      #6345415 - 01/30/14 03:26 PM

...the plastic-backed (not the sticky stuff): too stiff/thick to conform to the inside of the thin baffle tube of Apex 90/C90, I tried. Might work in Apex 127, though. Otherwise, this material performns admirably up to about 90 degrees incidence! The painted sandpaper seems a good idea, I will try it tonight in my Apex 90, C90 and Apex 127.

However, old question: Has anybody thougt of inserting a thin blackened spring, la Questar (see image)?

--Christian
Ottawa, Ontario


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ChristianG
sage


Reged: 10/18/12

Loc: Ottawa, Canada
Re: C90 Contrast Issue--Protostar flocking board... new [Re: ChristianG]
      #6345430 - 01/30/14 03:33 PM

Last thing... On my Apex 90, the corrector cell just unscrews. However, I haven't been able to do so with my C90--should I just keep trying or it's held differently (glue)?

Oh boy... I own too many of those Mak's: Apex 90, C90 Mak, Apex 127, Orion 180 and even a Questar 1978!!!

Plus I bought a Criterion 4000 just for the mount to make a 'poor man's Questar' with it and my Apex 90 just for fun. So you all see why I'd like to improve contrast on it...

--Christian
Ottawa, Ontario


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PowellAstro
scholastic sledgehammer
*****

Reged: 10/14/09

Loc: Tennessee
Re: C90 Contrast Issue new [Re: XyrcesFenol]
      #6345516 - 01/30/14 04:20 PM

Quote:

Late question on the successful baffle mod with black sandpaper that you did, was the improvment also seen at night? I belive the initial contrast test was during daytime, and if it helps in the dark I will do it myself too.




I got my Dad a C90 and have compared mine with the mods to his stock unit at night on Jupiter, Moon and Orion Nebula. I could very easily see the difference on all three objects. To my surprise, M42 shocked me. I could see what seemed to be 1/3 more nebula with the treated scope. Jupiter and the Moon was no contest and the difference made me not even want to look through the stock unit anymore. His will get all the treatment next.


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Sarkikos
Postmaster
*****

Reged: 12/18/07

Loc: Scotophobe Maryland, USA
Re: C90 Contrast Issue new [Re: PowellAstro]
      #6345700 - 01/30/14 05:54 PM

To those who have constructed a sandpaper or other type of contrast enhancement to fit into the primary baffle of the C90: Did anyone bother to note down the measurements? I assume this would be a rectangle that you fold into a cylinder. What were the dimensions - length and width - of the cylinder that worked best, without overlap and encroaching least into the light cone?

Mike


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Sarkikos
Postmaster
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Reged: 12/18/07

Loc: Scotophobe Maryland, USA
Re: C90 Contrast Issue new [Re: Sarkikos]
      #6345706 - 01/30/14 05:58 PM

Has anyone used the ProtoStar flocking paper for the baffle? I have plenty of that on hand. I don't have the flocking board. I don't think I'll be buying any of the flocking board just for this little project.

Mike


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PowellAstro
scholastic sledgehammer
*****

Reged: 10/14/09

Loc: Tennessee
Re: C90 Contrast Issue new [Re: Sarkikos]
      #6345707 - 01/30/14 06:00 PM

If the flocking paper is very thin, you should try it and let us know how it works. The sandpaper I used was around .007" thick.

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AhBok
professor emeritus


Reged: 12/02/10

Re: C90 Contrast Issue new [Re: PowellAstro]
      #6345757 - 01/30/14 06:35 PM

I made my sandpaper baffle with a piece 5" long and 1 & 7/8" wide. I cut it evenly with a paper cutter, rolled it into a tube with the edges touching and fixed it with a couple of small strips of clear tape. I then slid it into the baffle. It fit tightly, but not so tight that it would bend or fold. The result was a perfectly cylindrical tube. Mine made a huge difference. The rings from the glare of the moon or nearby stars made my C90 no fun to use at all. Now the rings are gone and the views are nice and dark.

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Sarkikos
Postmaster
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Reged: 12/18/07

Loc: Scotophobe Maryland, USA
Re: C90 Contrast Issue [Re: Sarkikos]
      #6346156 - 01/30/14 10:09 PM

Quote:

The rear opening is only 0.63"? That's only 16mm. Is it really that small? Looks like I'll have to get out my digital caliper this weekend.

Mike




I don't usually quote myself, but I had forgotten to measure the rear opening of my C90 until I reread my earlier post tonight.

So I got out the digital calipers this evening to measure the rear opening of my C90. I bought the C90 last year. Unfortunately, the rear opening was set too far back for my calipers to reach. But I measured as best I could by opening the calipers and sighting back at the rear opening of the scope.

Yes, the opening is approximately 16mm. All the other recent C90's should have the same measurement.

Mike


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Sarkikos
Postmaster
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Reged: 12/18/07

Loc: Scotophobe Maryland, USA
Re: C90 Contrast Issue new [Re: Sarkikos]
      #6346177 - 01/30/14 10:19 PM

While I was at it, I also measured the rear openings on my C6 and C5. The C6 is 25.6mm, the C5 is 24.5mm.

Mike


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Sarkikos
Postmaster
*****

Reged: 12/18/07

Loc: Scotophobe Maryland, USA
Re: C90 Contrast Issue new [Re: Sarkikos]
      #6346225 - 01/30/14 10:45 PM

I also measured the thickness of ScopeStuff flocking that I ordered not long ago. It is 0.32mm thick, according to my calipers. This includes the sticky-paper backing.

There was an earlier measurement for flocking in this thread, saying it was 1.78mm. That seems awfully thick. How could that be? If I set my digital calipers to about 1.78mm, the flocking - even with the paper backing - slips easily through with plenty of room to spare.

The 100 grit sandpaper was said to have a thickness of 0.009", or 0.23mm. That's only 0.09mm less than the ScopeStuff flocking. Will less than 1/10 of a millimeter make that much of a difference? I think I'm going to try the ScopeStuff.

Mike


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PowellAstro
scholastic sledgehammer
*****

Reged: 10/14/09

Loc: Tennessee
Re: C90 Contrast Issue new [Re: Sarkikos]
      #6346358 - 01/31/14 12:03 AM

It should be just fine. I am interested to see how it works. Some flocking is thicker than others and I had sandpaper on hand. Many years ago I used flocking in a reflector I built and it was almost 1/8" thick. This was almost 20 years ago though and I haven't purchased any for many years. Looks like the new stuff is much thinner.

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