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symmetal

RedCat 51 first image - Oh No!

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Hi JimothyC,

Yes, there is significant coma (fan shape smears pointing towards the centre of the image) in the bottom right and some coma top right and bottom left. It's more obvious in the brighter stars but if you look closely the dimmer stars do exhibit similar 'smearing'. Here's the CCD Inspector plot showing the same. Ignore the curvature/tilt analysis as it's interpreting the coma as star errors due to image curvature and tilt which it isn't. Just another poorly aligned RedCat I'm afraid. :frown:

JimothyC.thumb.png.6136c282f95f04b2b69d64f500f1d874.png

Alan

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Posted (edited)

Some coma at corners in brighter stars, top left looks OK, appears to be your average RedCat going by others images so guess it comes down to what you consider acceptable.

A few crops at X 200 and centre star which looks OK at X 400.

Dave

Untitled-1.thumb.png.eed777fb9e5b8fdb0ad1307c7d2cee2c.png

 

Edited by Davey-T

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From the point of view of testing just the lens surely it would be better to use the simplest imaging train, no filters and no long exposures like 30 seconds should be adequate. Otherwise any number of the other extras could be adding issues to the image.

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Thanks all for taking a look at this. Looks like the scope has got to go back. The issues with this scope appear quite prevalent. When you couple this with the fact that the vixen dovetail is undersized and the focuser isn't all that great, it's not looking like a great product launch from WO. You would have though they would have learnt from their previous mistakes, as should have I.

I feel sorry for the retailers in all this who'll have a lot of work on their hands dealing with all the returns and will probably end up absorbing some costs. 

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9 minutes ago, happy-kat said:

From the point of view of testing just the lens surely it would be better to use the simplest imaging train, no filters and no long exposures like 30 seconds should be adequate. Otherwise any number of the other extras could be adding issues to the image.

With the ASI1600MM, I think not having a luminance filter would have caused an issue as there would be no IR and UV filtering. Also if the scope can't cope with 36mm filters on a 4/3rds sensor, then it's not really fit for purpose.  

Exposures were 60 seconds, but the guiding was excellent, in fact I don't think I've ever seen the mount so happy. Probably due to it having such a light payload. 

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On 17/05/2019 at 15:25, symmetal said:

As Dave said a single image is all you need. As the coma, if present, is usually more evident on the edges of the image, a larger sensor (as on a DSLR) will show problems which may not be apparent on a small sensor.

If there is coma you can see it yourself visually when examining the image (especially in the corners) where the stars have fan shaped smears from the star centre. If you can't see any you're lucky and have a good lens.

A fits file is the normal file format from astro cameras and the fits file header includes useful information about the image but isn't necessary. From a DSLR just convert its output file to a tif or png file, which CCD Inspector can read. I'm not sure if it can read DSLR raw files. The CCD Inspector just gives a more accurate display of the star shapes/sizes though will interpret coma as a curvature/tilt problem though that is not always the correct interpretation. The coloured CCDI plot is very useful as a quick check that the image is good or has problems.

Alan

Thx for your replies mates!

Since Im waiting for my star adventurer being returned from RMA, my father had to take test exposures. Sky wasn´t 100% clear, but maybe the shots are good enough for evaluation?

60s exp with a Canon 80D:

https://drive.google.com/file/d/1Vg9ud-6eTGZdRFO2LVh95TZfXPEl3JfK/view

Would appreciate if you could tell me, if the RC needs to be recalibrated.

Henning

 

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47 minutes ago, Nubian said:

Would appreciate if you could tell me, if the RC needs to be recalibrated

Could you post as PNG to save downloading Tif

Thanks

Dave

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Looks pretty good, bit of coma in bottom right but if mine had been like yours I wouldn't have returned it.

Try to image a brighter denser starfield if you can as it will show up any faults better.

Dave

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2 hours ago, Nubian said:

Not sure if Im getting your point. You mean because of the size? ok, I attached a compressed png

It's just that png files, like jpg, display directly on the forum so don't need to be downloaded to view them. :smile:

As Dave said, slight coma, predominantly bottom right. Better than the other RedCat images shown here. Interestingly CCD Inspector gave it a 'good' result with all four corners similar and the centre slightly out of focus. Probably not enough stars for a proper assessment as it only found 523 stars. Around 3000 or more stars are needed fairly evenly spread over the image give the best results.

IMG3142_CCDI.png.93f8351a92982d1f68f48e7952a57a99.png

Alan

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I just got notified by OPT (Sorry, @FLO, I live in the states) that mine is shipping. Keeping my fingers crossed for a good unit. Of course, considering what you all have posted, I would honestly be happy with any of them compared to what I've been using which is just a Canon kit lens.

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13 hours ago, symmetal said:

It's just that png files, like jpg, display directly on the forum so don't need to be downloaded to view them. :smile:

As Dave said, slight coma, predominantly bottom right. Better than the other RedCat images shown here. Interestingly CCD Inspector gave it a 'good' result with all four corners similar and the centre slightly out of focus. Probably not enough stars for a proper assessment as it only found 523 stars. Around 3000 or more stars are needed fairly evenly spread over the image give the best results.

IMG3142_CCDI.png.93f8351a92982d1f68f48e7952a57a99.png

Alan

That looks pretty good, especially considering it’s an aps-c sensor. Has anyone tried one with a full frame one? 

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