M51 in one hour, and ten minutes (separately, on different rigs)

[AKB]

Last night, Feb 22, between about 9.00 and 10.00 PM.  The transparency and seeing wasn't as good as I had hoped for, but at least there was no moon.

I have my EEVA scope (f2.5, 9" Hyperstar) and my imaging scope (f7, Esprit 120ED) on the same mount and I thought it might be nice to compare short and rather longer exposures on these two.  Clearly, though, I haven't got them aligned quite right! 

Nonetheless, a creditable effort from the uncooled Ultrastar in 10 minutes, compared to 6 times that from the ASI294MC, and an endorsement for EEVA.  The colour image was, of course, subsequently processed a fair amount in PI.  The mono one, though, was collected in real-time using the excellent Jocular sofware by  @Martin Meredith.  This, I suppose, is the difference between f2.5 mono and f7 OSC.

I do need to take new flats for both.  Sorry about the image rotation.

Tony.

 

 

Edited February 23, 2022 by AKB

[AKB]

Just for the record, I got the flats sorted out...

MUCH better!

 

[Rodd]

The 120 hold up well to the Big boy--refractors rule,  

Why mask the hyperstar--what does that do?

 

[AKB]

A modest aperture mask is used to improve the tendency to bloat stars with the Hyperstar.  Marginally reducing the aperture slightly changes the effective diameter and therefore changes the focal ratio – in this case from f2.3 to f2.5.  Along with a curved former for the camera leads to remove diffraction spikes, this seems to give the Hyperstar a very acceptable performance in terms of star shape.  Certainly works for me in the EEVA application.  I think it looks pretty good for such a fast system.

Tony