Flea3 FL3-U3-13Y3M-C Mono Lunt Focus Issue

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04Stefan07
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Flea3 FL3-U3-13Y3M-C Mono Lunt Focus Issue

Post by 04Stefan07 »

I am having trouble getting my Flea3 FL3-U3-13Y3M-C Mono to focus with my Lunt50.

I have tried taking all adapters off and placing the camera directly on the BF but no luck (it's out of focus by a lot).

Is there anyway to get this camera into focus as I would like to use the cameras high FPS and resolution to capture some nice shots of the Sun!

Or am I better off finding if a ZWO camera can do the job?


SOLAR SCOPES: Lunt LS50THa Pressure Tuned with B600 filter & Moonlite Focuser, Daystar Quark Chromosphere
MOUNTS: Skywatcher HEQ5 Pro & Skywatcher Star Adventurer
CAMERA: Player One Neptune-M & Flea3 1.3 MP Mono USB3
Bruce Girrell

Re: Flea3 FL3-U3-13Y3M-C Mono Lunt Focus Issue

Post by Bruce Girrell »

I don't know if this may help or not.
The Lunt focus range is accomplished through two means: 1) the focuser, which has a fairly limited travel of about 30 mm and 2) the drawtube, which has a larger range of adjustment, about 75 mm. The two add to one another.

If you have been using only the focuser, then that is why you can't achieve focus. You need to loosen the screws that hold the blocking filter in place and slide the drawtube out to allow more focus adjustment. I usually set my focuser about midrange then, with the Sun visible (though out of focus) in the eyepiece (or on the computer screen, pull the drawtube out until the Sun is somewhere near focus. Anywhere the slightest bit close to focus is close enough. Lock down the BF screws and do final focus with the focuser.

BTW, I do screw my camera directly to the BF

Also I just thought of this - I use SharpCap for image capture. Usually when SharpCap comes up, the exposure defaults to a ridiculously large value (probably intended for DSOs). Even if the telescope is in focus, the Sun appears tremendously bloated and out of focus. It is impossible to focus until you get the exposure within range. Whether or not you use SharpCap, be sure that the exposure has been adjusted to produce a reasonable brightness before attempting any focus adjustment with the camera.


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Re: Flea3 FL3-U3-13Y3M-C Mono Lunt Focus Issue

Post by 04Stefan07 »

Bruce Girrell wrote: Mon Oct 16, 2017 7:16 pm I don't know if this may help or not.
The Lunt focus range is accomplished through two means: 1) the focuser, which has a fairly limited travel of about 30 mm and 2) the drawtube, which has a larger range of adjustment, about 75 mm. The two add to one another.

If you have been using only the focuser, then that is why you can't achieve focus. You need to loosen the screws that hold the blocking filter in place and slide the drawtube out to allow more focus adjustment. I usually set my focuser about midrange then, with the Sun visible (though out of focus) in the eyepiece (or on the computer screen, pull the drawtube out until the Sun is somewhere near focus. Anywhere the slightest bit close to focus is close enough. Lock down the BF screws and do final focus with the focuser.

BTW, I do screw my camera directly to the BF

Also I just thought of this - I use SharpCap for image capture. Usually when SharpCap comes up, the exposure defaults to a ridiculously large value (probably intended for DSOs). Even if the telescope is in focus, the Sun appears tremendously bloated and out of focus. It is impossible to focus until you get the exposure within range. Whether or not you use SharpCap, be sure that the exposure has been adjusted to produce a reasonable brightness before attempting any focus adjustment with the camera.
Thank you for that. I didn't think to move the drawtube out. I will try that once the Sun shows itself again and will report my findings.


SOLAR SCOPES: Lunt LS50THa Pressure Tuned with B600 filter & Moonlite Focuser, Daystar Quark Chromosphere
MOUNTS: Skywatcher HEQ5 Pro & Skywatcher Star Adventurer
CAMERA: Player One Neptune-M & Flea3 1.3 MP Mono USB3
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Re: Flea3 FL3-U3-13Y3M-C Mono Lunt Focus Issue

Post by 04Stefan07 »

That worked a treat!

I just need to buy a longer draw tube for it.

Is that something easy to get?


SOLAR SCOPES: Lunt LS50THa Pressure Tuned with B600 filter & Moonlite Focuser, Daystar Quark Chromosphere
MOUNTS: Skywatcher HEQ5 Pro & Skywatcher Star Adventurer
CAMERA: Player One Neptune-M & Flea3 1.3 MP Mono USB3
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Re: Flea3 FL3-U3-13Y3M-C Mono Lunt Focus Issue

Post by krakatoa1883 »

Do you need more focus travel inside or outside ? I had focusing problems with my Lunt50 & Chameleon CCD that I solved with an ultra-short T2-C adapter, but in my case the focus was too much inside.
Attachments
Adapter.jpg
Adapter.jpg (91.96 KiB) Viewed 1570 times


Raf
My solar images and reports with articles on solar equipment
Bruce Girrell

Re: Flea3 FL3-U3-13Y3M-C Mono Lunt Focus Issue

Post by Bruce Girrell »

04Stefan07 wrote: Wed Oct 18, 2017 9:32 am That worked a treat!

I just need to buy a longer draw tube for it.

Is that something easy to get?
Good! I'm glad I was able to get you headed in the right direction.
I would write to Lunt and see if they have a longer version or if they can give you specs that you can take to a machine shop to have one made. I have spent most of my time with microscopy and in that world it helps to develop a good relationship with a local machinist to make specialized pieces or to replace parts no longer in stock. I have a feeling that similar hardware customization issues exist in astro work.

You might also look for T-ring extension tubes. It sounds like you need just a bit more length from the drawtube. Since the BF contains no image forming optics, it won't matter if that extra distance comes before or after the BF, as far as the camera is concerned. You could screw the extension tube(s) on top of the BF and then attach your camera to that. The extension tubes shown in the photo below came with my ZWO ASI174MM camera. You might see if you can order the tubes separately.

06 ZWO spacer_1.jpg
06 ZWO spacer_1.jpg (1.04 MiB) Viewed 1537 times


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