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First Jupiter from the C9.25

JamesF

By JamesF
in Imaging - Planetary

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Freddie

Freddie

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Looking good James.

Not that I think you have a problem, but I find the 925 responds very well to perfect collimation. I use MetaGuide. Just set up ready for imaging and then fire up Metaguide for a quick check/adjustment then you're ready to image without the need to make any changes to the imaging setup.

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JamesF

JamesF

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Looking good James.

Not that I think you have a problem, but I find the 925 responds very well to perfect collimation. I use MetaGuide. Just set up ready for imaging and then fire up Metaguide for a quick check/adjustment then you're ready to image without the need to make any changes to the imaging setup.

Thanks, Freddie.  I do want to check the collimation at some point.  That might be easier than setting up my artificial star in the next county and trying to focus on it :)

James

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Virgoman

Virgoman

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Excellent first image from the 9.25 James and yes your last image is very nice indeed - plenty of detail and smoothly processed. :smiley:

                                    Best regards,

                                                             Ralph

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Space Cowboy

Space Cowboy

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I did.  The focal length is about 5m for this, but there's no rescaling or drizzle during processing.

In fact, I can work it out :)  The image is about 300 pixels wide, the camera pixels are 3.75um across and Jupiter is about 46 arcseconds wide at the moment, so that means the focal length is 206265 x 300 x 0.00375 / 46 = 5045mm :D

James

According to that equation I've been imaging at f18 not f24! Thought your image looked larger than mine James lol

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JamesF

JamesF

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According to that equation I've been imaging at f18 not f24! Thought your image looked larger than mine James lol

If you're using a 5x Powermate then I think I'd be wanting to check my maths first.  I'd say it's "unexpected" :) that a Powermate would give you f/18 in an f/4.7 scope.  With a barlow I'd be far less surprised.

James

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Space Cowboy

Space Cowboy

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I've been using a 3x tv barlow with the cam nose piece pulled part way out and was guessing that was giving me f18-20 but now I've measured it properly its actually only f16 and when I use an extension its f18 not f24 which I was getting with the DFK but I have been inserting the QHY cam body inside the extension tube which has been reducing the extension more than I realized.

One advantage of the QHY5L-II over the ASI120 is the 1.25" cam body allowing more flexible focal lengths. :grin:

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JamesF

JamesF

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Very nice James ... Are you still using firecapture or was that with your Linux program?

This was with FireCapture for the time being as I'm still sorting out all the mount control stuff etc. for Linux.  With observing opportunities so rare at the moment (and several of those lost to kit niggles) I just feel compelled to go with what I know works rather than risk having another night missed.  I'm still working on my capture application though.  I was hoping to get another release done last week, but work has intervened :(

James

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JamesF

JamesF

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I've been using a 3x tv barlow with the cam nose piece pulled part way out and was guessing that was giving me f18-20 but now I've measured it properly its actually only f16 and when I use an extension its f18 not f24 which I was getting with the DFK but I have been inserting the QHY cam body inside the extension tube which has been reducing the extension more than I realized.

One advantage of the QHY5L-II over the ASI120 is the 1.25" cam body allowing more flexible focal lengths. :grin:

Ah, yes, that would make sense.  A decent 1/2" sensor in a similar package would be great for solar Ha in the PST because it should avoid most of the problems with the lack of inwards focus that people have.  I'm not sure the Micron/Aptina sensors are up to the job though.

James

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SnakeyJ

SnakeyJ

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I've been using a 3x tv barlow with the cam nose piece pulled part way out and was guessing that was giving me f18-20 but now I've measured it properly its actually only f16 and when I use an extension its f18 not f24 which I was getting with the DFK but I have been inserting the QHY cam body inside the extension tube which has been reducing the extension more than I realized.

One advantage of the QHY5L-II over the ASI120 is the 1.25" cam body allowing more flexible focal lengths. :grin:

Interesting that you have found this as well Stuart, I've also noticed that the QHY5L-II consistently gives a lower focal length than you would expect with my barlows, even when clamped at the furthest possible extension with the barlow.     My Revelation x2.5 gives around x1.8 and my Baader Zoom x2.25 gives something like 1.8x (though fitted in a SW Delux x2 barlow tube).    The Revelation x5 gets closest at up to x4.6, though there is quite a lot of travel/extension possible in this barlow.

Is it possible the camera's optical window is having a slightly negative effect here or perhaps small production differences with the barlows in terms of spacing/location of the lenses?       I could do a quick test with a clear filter, though it's only a small discrepancy, of minor academic interest.      I generally use firecapture's ephems data from the preview screen during capture, which can fluctuate a little with seeing but the average over a session seems reasonably accurate if a planet is centred in the fov.   

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JamesF

JamesF

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Interesting that you have found this as well Stuart, I've also noticed that the QHY5L-II consistently gives a lower focal length than you would expect with my barlows, even when clamped at the furthest possible extension with the barlow.     My Revelation x2.5 gives around x1.8 and my Baader Zoom x2.25 gives something like 1.8x (though fitted in a SW Delux x2 barlow tube).    The Revelation x5 gets closest at up to x4.6, though there is quite a lot of travel/extension possible in this barlow.

Is it possible the camera's optical window is having a slightly negative effect here or perhaps small production differences with the barlows in terms of spacing/location of the lenses?       I could do a quick test with a clear filter, though it's only a small discrepancy, of minor academic interest.      I generally use firecapture's ephems data from the preview screen during capture, which can fluctuate a little with seeing but the average over a session seems reasonably accurate if a planet is centred in the fov.   

Looking at the ASI120MM and QHY5L-II I'd say that the sensor in the ASI120 probably can't get much closer than 15mm from the top edge of the barlow when you're using a nosepiece, whereas the sensor in the QHY is only about 5mm behind the metal part of the camera body and as such will probably be quite close to the top of the barlow if not actually inside it (though the camera does come with some extension rings, doesn't it?).  That might on its own be enough to make quite a difference in the effective multiplier for the barlow.

James

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SnakeyJ

SnakeyJ

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Looking at the ASI120MM and QHY5L-II I'd say that the sensor in the ASI120 probably can't get much closer than 15mm from the top edge of the barlow when you're using a nosepiece, whereas the sensor in the QHY is only about 5mm behind the metal part of the camera body and as such will probably be quite close to the top of the barlow if not actually inside it (though the camera does come with some extension rings, doesn't it?).  That might on its own be enough to make quite a difference in the effective multiplier for the barlow.

James

Good point James, though this short nosepiece and profile on the QHY5L-II does work to my advantage allowing me to image down to about 3.4x using the Revelation 5x barlow which is very close to the optimum F16.5 quoted for the 3.75um pixels.      The image train like this is considerably more solid and I have the option to slide the camera out to get 4.6x (F23) should we ever get some of the near mythical excellent seeing.

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