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Mirror shift?

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#1 James Cunningham

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Posted 25 October 2012 - 08:35 AM

Is there any way to easily prevent mirror shift? Thanks.

#2 rigelsys

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Posted 25 October 2012 - 06:10 PM

No. Not when using the focus knob (which moves the mirror) to focus.

The only alternative is to use a separate focuser (e.g., crayford or other) and leave the CPC focus knob alone.

#3 Digital Don

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Posted 25 October 2012 - 10:04 PM

The only way to eliminate mirror shift when focusing is to use and external focuser. I installed a FeatherTouch on my CPC 1100 and get absolutely no shift while focusing because the mirror remains stationary.

The 'cover' over the original focus knob is the cap from a spray can. it was painted with Rustoleum textured spray paint which is almost a perfect match to the finish and color of the scope. It was attahced by wrapping a strip of foam around the original knob and pressing the cap in place.

Don :usa:

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#4 James Cunningham

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Posted 26 October 2012 - 05:45 AM

So, you don't have to get a rough focus with the scope's regular focuser first and then fine tune it with the feather touch? I have a feather touch too but mine replaced the regular focuser and I still get shifting when I focus.
Jim

#5 Digital Don

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Posted 26 October 2012 - 05:12 PM

I adjusted the original focuser so that focus was reached with the FeatherTouch drawtube half way out. All focusing -at least for my particular setup - can be accomplished using only the FeatherTouch knobs. I don't have to touch the orignal focuser.

You mention that you also have a FeatherTouch but it sounds like you have the 'microfocuser'. I also tried one of those and like you, still got image shift so I returned it and purchased the Crayford version shown in the picture above.

Don:usa:

#6 Peter in Reno

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Posted 26 October 2012 - 05:28 PM

Hi Don,

Can you use external Crayford focuser for wide range of eyepieces like between 4mm and 31mm without touching the original or stock focuser?

Peter

#7 Gastrol

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Posted 26 October 2012 - 05:39 PM

I also have the FT Crayford type focuser on my SCT and all my ep's (1.25 and 2 inch) reach focus without having to touch the stock focus knob. And my FT focuser is the short profile version which comes with the shorter 0.8" drawtube vs the standard 1.5" drawtube.

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#8 Digital Don

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Posted 26 October 2012 - 09:22 PM

Hi Peter,

The shortest focal length I might use (and not very often) is a 7mm Nagler, the longest is a 24mm Panoptic. There is enough focus travel to accommodate both.

However the reality is that I have basically stopped using eyepieces since purchasing a MallinCam. Other than compensating for mirror movement when pointed to different arreas of the sky, I rarely have to do much focusing even with the FeatherTouch.

Don:usa:

#9 dragonslayer1

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Posted 28 October 2012 - 10:02 AM

Don, was wondering if could ask you something about the Mallincam. Are you just able to scan the stars and sky as if with a E/P and see the "sky" as you would with an E/P or does the Millincam just like a CCD in that it takes time for it to gather the info it is seeing? Would it clear the forks on a CPC 9.25? I understand the CPC 11 has more clearance than the 9.25. To be able to eliminate mirror shift would be awesome. Thank you

#10 barbarosa

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Posted 28 October 2012 - 02:35 PM

Don, was wondering if could ask you something about the Mallincam. Are you just able to scan the stars and sky as if with a E/P and see the "sky" as you would with an E/P or does the Millincam just like a CCD in that it takes time for it to gather the info it is seeing? Would it clear the forks on a CPC 9.25? I understand the CPC 11 has more clearance than the 9.25.


I can't speak to the Malincam, but the two CCD security cameras that I use work fine for alignment. For fainter stars, I bump the integration up to 2x or 4x, sometimes a bit more. I don't scan the way I might with an EP because even with stacked reducers the TOV is less than .5 degree.
I use the cameras 95% of the time now.

I just measured a CPC1100 and a CPC925, and the clearance from the locking knob, when locked down, to the rear cell is ~8.5" on the 11 and ~9.75” on the 9.25.

#11 James Cunningham

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Posted 28 October 2012 - 02:49 PM

What kind of cameras do you use?

#12 barbarosa

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Posted 28 October 2012 - 05:24 PM

What kind of cameras do you use?

Same as you, sir. ;)

#13 dragonslayer1

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Posted 28 October 2012 - 06:20 PM

Thank you David, That sheds some light on it. For me sometimes just like to slowly rotate my scope thru the sky, no particular target but just observing the heavens as it scrolls and just view it. Wondered if with a video cam would offer same real time viewing. Your not the first one that says hardly uses E/P now that have video cam. Have also been reading is much easier to capture pictures for viewing or showing later, much easier than standard CCD camera to get to finished product. Did you ever follow up on the Telrad for targeting? Kasey

#14 Digital Don

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Posted 28 October 2012 - 06:23 PM

Don, was wondering if could ask you something about the Mallincam. Are you just able to scan the stars and sky as if with a E/P and see the "sky" as you would with an E/P or does the Millincam just like a CCD in that it takes time for it to gather the info it is seeing?



If you want to use it "live" you can turn Sense up to OFF, set the sync to VBS, and use the shortest available integration time. When you do that, you will see the star images moving on the monitor screen as you move the scope, similar to what you'd see in an eyepiece.

Set up like that however, no deep sky objects will be visible. To capture deep sky objects, you need to increase the integration time and adjust other settings. The picture of M 1 on the right shows what I saw on the monitor. It was taken using a 'point and shoot' camera. The MallinCam was set for less than a minute integration time and no filters were used. I live roughly 50 miles south of Chicago so that will give you an idea what my skies are like.

On my setup, I use a FeatherTouch focuser and a 2" diagonal as shown in the left picture below so there is no interference with the camara and the base.

Don:usa:

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#15 barbarosa

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Posted 28 October 2012 - 07:29 PM

Thank you David, That sheds some light on it. For me sometimes just like to slowly rotate my scope thru the sky, no particular target but just observing the heavens as it scrolls and just view it. Wondered if with a video cam would offer same real time viewing.

You are quite welcome Kasey.

If I just want to look around I put in my Meade 5000 SWA 20mm and sometimes a focal reducer. If I plan to scan, I put my C5 on a Polaris mount in Alt-Az mode.

There are some image quality tradeoffs with these cams, but for DSOs they are definitely worth it.

Last night I watched Jupiter on my laptop via the CPC1100, an LN-300 and a 2X Barlow. ~550X and kind of jumpy, not too bad but not good either. It was a bit better without the Barlow. The view on a great night through a good EP is better, but I don’t get many of those. Just for fun I pulled out the camera and put in a 6mm ortho w/ barlow. It was a bright, low contrast view and not sharp view. I preferred the image in the cam. I pulled off the Barlow, but still un-sharp and low contrast. I tried filters and they helped, but I had to go above a 12mm EP for a better view.

I think I can put it this way I like the camera for anything with color, or that is difficult or impossible to see in my suburban sky and sometimes the cam is good for globular clusters and faint companion doubles.

Did you ever follow up on the Telrad for targeting? Kasey


I decided to stick with a finder scope for the time being. I will move a SV F50 to the CPC1100 and see if I can rig the illuminator to run from the mount supply.

#16 James Cunningham

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Posted 28 October 2012 - 07:54 PM

I can use the Mallincam to get an alignment but have not been able to do so with the other cameras. How do you do that?

#17 dragonslayer1

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Posted 29 October 2012 - 09:57 AM

Thank you David and Don, think will go with Video cam, know there is big price difference between products used in this topic so far. Don, is that the extreme model you have? And have either of you tried a filter wheel in front of camera and/or focal reducer? Thank you for the brain trust sharing, Kasey

#18 Digital Don

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Posted 29 October 2012 - 06:17 PM

Hi Kasey,

My MallinCam is a VSS+. For me, the main appeal of this model is that you can operate it with or without a computer. The Xtreme has additional capabilities and functionality, but requires a computer to access them.

I typically use my camera in the observatory and can easily control it with a computer, but doing so adds an unnecessary (for me) layer of complexity so I don't bother. Plus, if I take the MallinCam to a remote site, I don't have the power requirements of a laptop in addition to the rest of the equipment.

I've tried various filters and they do work. However, what seems to work better for me is increasing the gain while using shorter exposure times.

Don :usa:

#19 dragonslayer1

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Posted 29 October 2012 - 08:07 PM

Hey Don, this will sound real stupid, but how do you view what your filming without a laptop or monitor of some kind? The thought of lugging laptop around to star parties or for sharing viewing is not appealing as well as the necessary power supply. When am able to make star parties or neighbors drop by always wish had a better way to share, at home use front driveway so power for computer is no problem.. You seem to have a nice set up with observatory and all. Kudos to you, thanks Kasey

#20 Digital Don

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Posted 29 October 2012 - 11:48 PM

Hi Kasey,

Thanks for the kind words!

The MallinCam outputs two video signals - composite video and S-Video and both can be used simultaneously. To view images produced by the camera, you need a monitor with corresponding inputs, or a computer with an adapter. In my observatory, I use a 9" Speco CRT monitor which works very well.

As nice as the Speco is, I don't consider it practical for field use since it requires A/C power and weighs about 15 pounds. When I take the MallinCam to a remote site, I use a 'Digital Prism" 9" LCD TV. It's not as nice as the Speco - but quite acceptable - AND much more practical since it only weighs a couple of pounds, and can be powered by it's own internal battery or any 12 volt source. I purchased mine a couple of years ago at Office Depot for $80.

Don:usa:

#21 barbarosa

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Posted 30 October 2012 - 09:22 PM

Thank you David and Don, think will go with Video cam, know there is big price difference between products used in this topic so far...have either of you tried a filter wheel in front of camera and/or focal reducer?


I have not used a filter wheel, although I sometimes do use an LPR or 03 filter. When I use a filter and a .5x reducer I sometimes put the filter between the reducer and the c-mount adapter to get a slightly more reduction and a wider FOV.

#22 barbarosa

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Posted 30 October 2012 - 09:28 PM

I can use the Mallincam to get an alignment but have not been able to do so with the other cameras. How do you do that?

Jimmy I don't know if you can hijack your own thread but I think we are turning this one toward Cuba.

First clear night (hopefully by Saturday) I will try alignments with both cameras and with/without a focal reducer. I have both a .5x and the Celstron f/6.3 and if you prefer one particular setup send me a PM. If conditions (including my back) are marginal i might use a C5 but you should be able to scale the settings for your 11.






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