A few images taken with SDM Dob

[danielsun]

Love all of your work Alex, from your photos to your time lapses.

Cheers Daniel.

[alexch (Alex)]

Originally Posted by Satchmo

Thanks Alex. Great links. It makes sense as the star is a blob of light at the focal plane that is swollen by seeing , tracking errors and optical errors. At the end of the day its a photon stream that increases in brightness with aperture. Just out of interest what is your scale of pixels /arc second with this camera /scope combination and what sort of FWHM were you getting on the night you took these exposures ?

The FOV calculator tells me I can fit 0.6x0.4 degrees onto SONY Nex-5 chip with Paracorr and 2360mm FL. Judging by the moon it is right.

So I have 4592 pixels covering 2160 seconds of arc, which works out to be 2.125 pixels per arcsecond.

For "Centaurus A" my DeepSkyStacker image parameters were:
FWHM=8.36, Sky BAckground=10.16%

Cheers,
Alex

[alexch (Alex)]

Dave, prokyon, Paul, Stacey, Lester, clem and Daniel - thanks heaps for the comments!

[toc (Tim)]

These are amazing!

How long will it track before tracking errors are apparent?

[alexch (Alex)]

Thanks, Tim.

10-15 seconds before the errors come in, depending on the part of the sky. The closer to zenith the worse.

[CometGuy]

Hi Alex that is great work!

I had a look at your ghost of Jupiter image and the image scale is around 0.5" / pixel. Its impressive your getting tight star images with 10 second exposures (as well as mag 18 stars). All I can say is wow!

Terry

[stutir (Stuti)]

Hi Alex

You have mentioned about SONYNex5 for capturing the images. Please let me know if I can also go ahead and make this investment for astrophotography for my SKYWATCHER 150750 EQ 3-2.

Please suggest.

Thanks and regards

Stuti

[HRJ (Harshad)]

Awesome images Alex.

Originally Posted by alexch

Also the Servocat Alt-Az motors want to correct the pointing every now and again and limit the exposure time to no more than 15 seconds.

What does this mean? I am not familiar with Servocat. Does it mean that the tracking motors kick in only once in about 15 seconds? In other words, your sub-exposures aren't tracked and have minute (invisible) trails?

[alexch (Alex)]

Originally Posted by CometGuy

Hi Alex that is great work!

I had a look at your ghost of Jupiter image and the image scale is around 0.5" / pixel. Its impressive your getting tight star images with 10 second exposures (as well as mag 18 stars). All I can say is wow!

Terry

Thanks Terry. My calculations were the same: 2.125 pixels per arcsecond. That large aperture is good to have

[alexch (Alex)]

Originally Posted by stutir

Hi Alex

You have mentioned about SONYNex5 for capturing the images. Please let me know if I can also go ahead and make this investment for astrophotography for my SKYWATCHER 150750 EQ 3-2.

Please suggest.

Thanks and regards

Stuti

Stuti, Sony NEX-5 is a good camera, that can do general day-time photography and also used occasionally for astro-photography. However I wouldn't recommend to purchase it just for astro work, because:
1) It does not have an optical viewfinder and. In my 22" the stars are quite bright on the screen but it may not be the case for smaller telescopes
2) The body is small and the sensor is being constantly used for live view and NEX cameras are getting warm very quickly. IT will be a problem with longer exposures required with smaller telescopes.

Hope it helps.
Alex

[alexch (Alex)]

Originally Posted by HRJ

Awesome images Alex.



What does this mean? I am not familiar with Servocat. Does it mean that the tracking motors kick in only once in about 15 seconds? In other words, your sub-exposures aren't tracked and have minute (invisible) trails?

Thanks.
Servocat is a drive system for Alt-Az mounts and needs to correct for field rotation.