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Focal reducers and a LX200 12"GPS

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#76 cold space

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Posted 27 July 2008 - 06:43 AM

Hi all,
I finally received my Optek .33 maxfield reducer and Optek mallincam "c" thread adapter after a 3 week wait. I had a chance for about an hour or so last night before the clouds rolled in.
I attached it to the front of the Mallincam and inserted it into the 2 inch diagonal of my 12 inch LX200R scope as the reducer has a 2 inch barrel.
What can I say, the views of M16, Lagoon, Omega centaurus were spectacular. Far better than when my scope was running at about F5.5 for these objects. The field size look similar to what greg was posting of M16 a few weeks back.
Plenty of detail in these objects, far more than Iwas getting at F5.5.
As usual the clouds came in so had to call it a night.
I have received a couple of PM's from people regarding this reducer so I am sorry I can't post any images at the moment as I have only just got my capture device and are still yet to work it all out, but don't worry, I will be going on holidays tommorow for a week away so I will give Gavin this reducer to try out on his 14 inch LX200R while I am away so I am praying for good weather this week for him and hopefully he can capture a couple of images to show you guys. One more note,
I tried my Optek 2 inch F7 reducer in the diagonal and had attached the Optek 3.3 reducer to the back of it via a tube type connector I had made up and then to the Mallincam. I got stars up on the screen but ran just short of focus travel then it clouded up.
When I get back from holidays I will try this again without either the micro focuser or the diagonal to see if I can get focus and any sort of acceptable wide field image. Will keep you posted.

Regards Matt.

#77 Gavin Bray

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Posted 29 July 2008 - 06:47 AM

Matt kindly lent me his Optec NextGEN MAXfield 0.33X FR and I had a brief session with my 14" LX200R before the clouds rolled in.

I'm very happy with the results and would rate this FR better than my MFR-4 and Matt's MFR-3. Although not designed for the ACF SCTs, when used with the Mallincam's relatively small chip I could see no image degradation.

I also measured the actual focal reduction. With my MFR-4 I only get about 0.5 instead of the advertised 0.33. However, with the Optec I'm definitely getting 0.33.

If anyone's looking for a good 0.33 FR I would certainly recommend the Optec.

If the weather cooperates I will also try Matt's Optec 0.7 FR and a combination of both FRs and report back.

Gavin

#78 Rob Lambert

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Posted 01 November 2008 - 03:00 PM

Guys,

I just bought a 10-inch LX200GPS with Mallincam from a LVAS club member that is taking a break from astronomy for awhile, so I'm just learning how to use it. I've already learned a lot from this thread, and appreciate the experience you've shared.

My MCHP has a MFR3 with what I think is a 10mm spacer. I didn't see a MFR4 on the Mallincam website; is it still available?

In my initial observations, I've noticed that I obviously need some more reduction for a lot of the objects I would like to observe. For example, the Flame Nebula more than filled the FOV with just the MCHP and the MFR3 with spacer. I plan to purchase another 10mm spacer to provide another reduction option, but I don't think that will be enough for some objects. My optical path is a little long with a microfocuser, a diagonal, and a flip mirror (see attachment) and adding a 10mm shouldn't add any more length to the path.

For further reduction, would it be better to place a Meade/Optec 6.3 or 3.3 FR between the Mallincam and the diagonal or between the diagonal and the back of the OTA?

I really like being able to use the flip mirror and need the diagonal to prevent hitting the mount with the camera. Any additional guidance or considerations would be appreciated.

Rob Lambert
President, Las Vegas Astronomical Society

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  • 2729980-Robs Setup.jpg


#79 Rob Lambert

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Posted 01 November 2008 - 03:02 PM

Here's a blowup of the optical path.

Rob

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  • 2729983-Optical Path Blowup.jpg


#80 Jack Huerkamp

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Posted 02 November 2008 - 09:03 PM

Rob,

I use a Celestron f/6.3 FR on the back of the OTA and a MallinCam MFR-3 and 10mm ER in the camera to get to about f/4.

The MFR-4 is no longer available due to a shortagae of one of the needed lens assemblies.

Jack

#81 Rob Lambert

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Posted 03 November 2008 - 01:59 AM

Thanks, Jack.

I picked up a Lumicon .5 FR yesterday because of the various connectors I have along the optical path. I found out tonight that I can't reach focus with everything I have in the path. When I removed the flip mirror, I was able to reach focus and was quite pleased with what I was able to see in the bright lights of Vegas. I may take the Lumicon FR back and swap it for the Celestron, if that will allow me to reach focus with the flip mirror in the path. It really is handy to use the mirror for EP and Video assisted observing. I was surprised to see that I could observe the Little Dumbell and M82 from Vegas. I normally can't see them with just an EP.

Waiting on my Speco VM905C to arrive - using a DVD player right now - not much contrast.

Thanks for the info on the MFR4 and all of the other info you've provided this forum.

Will stay in touch with you guys.

Rob

#82 Jack Huerkamp

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Posted 03 November 2008 - 08:03 AM

Rob,

I used my Speco VM905C and a 10" DVD player at a stargaze this past week. There is no comparison in the views provided. You will really appreciate what the Speco will provide. Also, there is a trim-pot on the back of the unit that allows for adjustment of the brightness level that allows you to go darker or brighter as needed. Depending on sky conditions, it can be very useful.

Jack

#83 smokin oakum

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Posted 05 November 2008 - 09:34 AM

Post deleted by smokin oakum

#84 Jack Huerkamp

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Posted 05 November 2008 - 01:13 PM

Neil,

I have used the f/6.3 on the OTA and the MFR-3 and 10mm ER on the camera on both my C-8 and on my CPC1100.

The Moonlite setup with internal focal reducer capabilities shuld work as well.

Jack

#85 smokin oakum

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Posted 05 November 2008 - 07:09 PM

The best part about this fix while running straight through is, the focal reducer remains the same distance away from the CCD, and will stay the same way while focusing.

Neil

#86 Rob Lambert

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Posted 13 November 2008 - 03:25 PM

Unless I just missed it, I didn't see a post concerning the formula for determining the exact focal ratio for a combination of focal reducers. Is there such a formula that takes you beyond multiplying the scope's f/r by the focal reducer's f/r or reduction rate; something that takes into account the distance between focal reducers and the distance to the sensor? I would like to accurately determine the f/r with my combination of Celestron 6.3 fr with the Mallicam MFR3 with the 5mm and 10mm spacers and a Meade 647 flip mirror separating the two on an f/10 SCT. I just don't know what the basic formula is for computing the change in f/r.

Thanks,

#87 mclewis1

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Posted 13 November 2008 - 10:59 PM

Rob,

I don't know about any formulas but each focal reducer does have a "sweet spot" so to speak of distance or spacing where they provide the best image. Unfortunately every type of focal reducer seems to be different.

The Celestron F6.3 was originally designed for use with 35mm cameras and seems to have a sweet spot of 100-110mm, although some folks claim to get better images with a spacing of 80-90mm (which seems to deliver a reduction of around .75x). The smaller OPT 1.25" F5 unit that you saw in my other thread works well with a 25mm spacer between it and the MC sensor, and this seems to deliver about .6x.

The third variable is enough focus travel to get the whole combination to come to focus and getting that F6.3 unit as close to the rear of the scope is one way to address this issue. Or to put it another way the farther away the F6.3 unit is from the rear of the scope the less likely you're going to have enough focuser travel to bring the whole thing to focus. This is why Jack and others recommend the external Moonlite focuser ... it has the ability to mount the F6.3 unit up inside it instead of behind it.

I'm afraid that with your combination that the 2" diagonal will likely cause you problems. It will add something like 4+ inches to the optical path by itself, so in combination with any other components (flip mirror, etc.) the F6.3 reducer likely won't work. Plus you'd need an SCT - 2" barrel adapter to use the F6.3 unit with your diagonal or microfocuser.

One possibility with your setup might be a 2" focal reducer that would thread onto the nose piece of your diagonal (2" eyepiece/filter threads). I don't know where that 2" unit will come to focus but I think that the 6+ inches of 2" diagonal plus the flip mirror will not work. It might however be ok without the flip mirror.

#88 Rob Lambert

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Posted 14 November 2008 - 01:25 AM

Mark,

The Celestron 6.3 FR screws onto the scope side of the flip mirror and with a 2" extension tube the FR slides into the diagonal. I haven't measured the distances between the two FRs. I think I have the Celestron 6.3 FR as close to the scope as I can get it, right now. I currently don't have a way to put it on the scope side of the diagonal and with the Peterson Eyeopener on the back of the SCT, I almost have to have the microfocuser to connect anything to the scope. I can just bring it all to focus, but the focus is all the way in and I have a hard time telling that the microfocuser makes any difference at that point. The latest images I posted on Yahoo were captured with this setup.

Straight forward calculation would yield a theoretical f/r of 3.75, but I don't think that is correct for this setup, that's why I was interested in a formula for computing the f/r.

I'm going to work with some different adapters to see if I can change the location of the 6.3 FR and get it in front of the microfocuser. It's been a while since I've dabbled in physics and I'm enjoying this from several angles.

Take care.

#89 mclewis1

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Posted 14 November 2008 - 11:13 AM

Straight forward calculation would yield a theoretical f/r of 3.75, but I don't think that is correct for this setup, that's why I was interested in a formula for computing the f/r.


Rob, Interestingly that F3.75 number is about what I now get with my combination of the F6.3 and F5 focal reducers. Originally I was around F3.4 but I cut down one of the 1.25" adapters on my flip mirror (which moved the MC and FR about 25mm closer to the F6.3 reducer) to improve the image quality a bit and to shorten/stiffen the whole setup.


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