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Use submitted images on az mount confusion


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Hi everyone got a reasonably obvious question regarding basic equipment for imaging.

I know you need a guided eq mount for astrophotography but on the celestron website they have some lovely goto az mounted scopes with wonderful images which claim tb user submitted..

Does this mean you can still get gd images with the az set up!? As long as its motorized? Even dsos have been captured.

Thanks, hope to clear up this confusion

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Looking at the site some of the images have been taken with the fork mounted scopes used with an additional wedge which allows the scope to be polar aligned. The alternatives if you do not wish to use a wedge (and many are not complimentary about them) is you can use software to de-rotate the field rotation inherent in an Alt Az image (which limits the sub exposure time to very short ones), or you can purchase a fairly sophisticated piece of equipment called a Field De-Rotator which attaches to the back of the scope and counters the field rotation by rotating the camera during the exposure.

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Hi guys, thanks for the replies and sorry I didn't acknowledge sooner!

it this one any good, which I quite easily captured with a compact camera on the Celestron SLT mount?

sgazer, this is more than good my friend! I think you should post this to anyone who insists that only a guided EQ mount is mandatory for AP!

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Looking at the site some of the images have been taken with the fork mounted scopes used with an additional wedge which allows the scope to be polar aligned. The alternatives if you do not wish to use a wedge (and many are not complimentary about them) is you can use software to de-rotate the field rotation inherent in an Alt Az image (which limits the sub exposure time to very short ones), or you can purchase a fairly sophisticated piece of equipment called a Field De-Rotator which attaches to the back of the scope and counters the field rotation by rotating the camera during the exposure.

Sounds interesting but very complex for a novice like me!

Maybe one day, however I am still biased towards the Eq mount

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Sounds interesting but very complex for a novice like me!

Maybe one day, however I am still biased towards the Eq mount

Quite right. The reason big observatories use ALT-AZ mounts is that the cost of the de-rotator is far less than the cost of the mount and building to house the scope.

Looking at "low cost" de-rotators

http://www.optecinc.com/astronomy/catalog/pyxis/pyxis.htm

they cost about the same as an EQ mount and are probably a lot of unnecessary hassle.

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I think the images on that site may well be made with the SLT without wedge. The only nebulae on it are very bright. If you take images of these when they are due south, field rotation may not be so severe that a series of exposures of a couple of minutes could not be stacked to get these results. An EQ mount is better of course.

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The short answer is yes, you can image DSOs with a tracking alt-az scope. You are limited by field rotation to exposures of ~30s-2min depending on where you are pointing in the sky - but DSOs are perfectly doable with these sorts of exposures. You just need to stack a lot of them. The extra read-noise from each time you read out the camera means you will not do as well in the same total time as someone doing longer individual exposures on a guided EQ mount, but the effect of this is often exaggerated, especially for those who image in light polluted skies.

NigelM

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