The Squid with RASA8 and OSC - first two hours

[gorann]

After a month of constant clouds I managed to get 27 x 5 min (so 2.25 hours) of data on the Squid and Bat nebulae last night. As everyone (here) knows this is an extremely faint object so I had no expectations more than maybe to see if it would be worth while to do it properly with many hours. While being clouded in I have as usual been shopping, so the RASA 8 is now sitting on an iOptron CEM70. The ASI2600MC is attached to the scope with a new dedicated adapter from Artesky (less flimsy than the supplied Celestron one) that also has threading for a 2" filter. So in there I put a new filter, an IDAS NBX dual band (Ha + Oiii) filter that is made for fast systems like the f/2 RASA. Maybe the Artesky adapter is the reason I could not see any annoying amount of tilt this time.

Here is the result. I aim/hope to get more data over the next few nights but I think this proves that the RASA 8 is a real light bucket, the ASI2600MC is a very sensitive camera, and that dual band filters work quite well on OSC cameras.

And, yes it is very very faint - I think I got stretch marks from doing this one🥴

Time to buy an OSC Olly @ollypenrice? 😁

PS. That little blue and red baby squid down in the right corner is real and not a reflection in the optical train.

Edited November 20, 2020 by gorann

[carastro]

Amazing from a OSC and 2.5 hours.  If l have read it properly.  
 

carole

[gorann]

Just now, carastro said:

Amazing from a OSC and 2.5 hours.  If l have read it properly.  
 

carole

Thanks Carol! 2 hours and 15 min😉

[geordie85]

That's amazing for such a short integration time. You must have pretty dark skies.

I tried this a few years ago with 30 minute subs and got nowhere near this.

[gorann]

2 minutes ago, geordie85 said:

That's amazing for such a short integration time. You must have pretty dark skies.

I tried this a few years ago with 30 minute subs and got nowhere near this.

Yes, some nights I can get an SQM of 21.6, so Bortle 2-3, but last night was not as great with an SQM of 21.1 and poor seeing. But an FL of 400 mm is quite forgiving and f/2 helps a lot.

[tooth_dr]

And this is why I have the dilemma over OSC or mono.  Obviously it helps being in a dark location, but these results are just incredible, and I wonder if the hassle of mono and EFW is worth it.

Edited November 20, 2020 by tooth_dr

[MartinB]

Fantastic image Goran!

2.25hrs with an F2 8" scope = a lot of photons.  Attached to a sensitive camera and hey presto!  I wouldn't like to use a mono camera with that scope.

[Laurin Dave]

Very nice Goran, your dark skies must help with a OSC..  that object lower right is a jellyfish by the way  

Dave

[gorann]

2 minutes ago, tooth_dr said:

And this is why I have the dilemma over OSC or mono.  Obviously it helps being in a dark location, but these results are just incredible, and I wonder if the hassle of mono and EFW is worth it.

Fortunately Adam I am at a quite dark place so would not know how well it works under light pollution, but a dual band filter like I used on this one could probably work quite well.

[MartinB]

Have I got the sums right.  Isn't 2.25 hours at F2 achieve the same light grab as 9 hours at F4 with a scope with the same aperture.   Or 36 hours at F8!

[tooth_dr]

Just now, gorann said:

Fortunately Adam I am at a quite dark place so would not know how well it works under light pollution, but a dual band filter like I used on this one could probably work quite well.

Cheers Goran, I fortunately dont live in the city/town either, hence my uncertainty about sticking with mono, or taking the 'backward' step to OSC.

[gorann]

3 minutes ago, MartinB said:

Fantastic image Goran!

2.25hrs with an F2 8" scope = a lot of photons.  Attached to a sensitive camera and hey presto!  I wouldn't like to use a mono camera with that scope.

Thanks a lot Martin! I have actually previously used it with an ASI1600MM and filter slider for Ha and it does work, but doing mono with RGB filters would defenitively not be worth the effort.

[gorann]

1 minute ago, tooth_dr said:

Cheers Goran, I fortunately dont live in the city/town either, hence my uncertainty about sticking with mono, or taking the 'backward' step to OSC.

I think you may consider the new CMOS OSC a step foreward😉

[ollypenrice]

Yes, no question. That's a stunning setup. I'm quite prepared to accept that the OSC rule book has been re-written by modern cameras and have said so already. The dual band filter has also done a brilliant job. The old technology can't get near this in the time. Also very importantly, you have nice tight, shapely stars throughout. The RASA strikes me as being in a different class to the Hyperstar.

Olly

[ollypenrice]

7 minutes ago, MartinB said:

Have I got the sums right.  Isn't 2.25 hours at F2 achieve the same light grab as 9 hours at F4 with a scope with the same aperture.   Or 36 hours at F8!

In my view there's nothing wrong with comparing F ratios and exposure times in this way if the focal length is constant, the variable is aperture and the pixels also remain the same size. 

Olly

[gorann]

13 minutes ago, ollypenrice said:

Yes, no question. That's a stunning setup. I'm quite prepared to accept that the OSC rule book has been re-written by modern cameras and have said so already. The dual band filter has also done a brilliant job. The old technology can't get near this in the time. Also very importantly, you have nice tight, shapely stars throughout. The RASA strikes me as being in a different class to the Hyperstar.

Olly

Thanks Olly! I cannot wait to see what it can do with 5 - 10 more hours, but tonight is cloudy again and it is Friday which for me and the wife means fresh langustines from Gothenburg and white wine 🥂🦞

Saturday night looks promising AP wise right now

Edited November 20, 2020 by gorann

[tooth_dr]

11 minutes ago, gorann said:

I think you may consider the new CMOS OSC a step foreward😉

Indeed   hence the ' ' lol  

Again what an incredible image for just two hours.

 

[gorann]

16 minutes ago, MartinB said:

Have I got the sums right.  Isn't 2.25 hours at F2 achieve the same light grab as 9 hours at F4 with a scope with the same aperture.   Or 36 hours at F8!

Maybe you mean same focal length? An Esprit 80 with a 400 mm FL (so f/5) would need (5x5) / (2/2) = 6.25 times more time than the RASA8 with 400 mm at f/2.

[tomato]

Awesome result,  so glad I saw your post and went for the NBX rather than the L-extreme filter. Good to hear the solid adapter is a better option than the Celestron item, looks like my custom QHY adapter should be threaded to take the filter, rather than install it in the RASA optical window.

[Mr Spock]

Very impressive image. That RASA is an equally impressive scope.

[MartinB]

24 minutes ago, ollypenrice said:

In my view there's nothing wrong with comparing F ratios and exposure times in this way if the focal length is constant, the variable is aperture and the pixels also remain the same size. 

Olly

Ooops, quite right, slip of the keyboard.  Yes, it is the focal length that remains constant.  The light gathered is a function of the aperture not the F ratio!

[geordie85]

1 hour ago, gorann said:

Yes, some nights I can get an SQM of 21.6, so Bortle 2-3, but last night was not as great with an SQM of 21.1 and poor seeing. But an FL of 400 mm is quite forgiving and f/2 helps a lot.

Still alot better than my bortle 6 skies.

[carastro]

Quote

some nights I can get an SQM of 21.6, so Bortle 2-3

I guess that must have something to do with it as well as the speed of the optics.  I can never get to anything less than Bortle 4.

Carole 

[Mick J]

Wonderful picture and description Gorann (enjoy your supper - you have earned it), I cannot add to any of the above comments, I can only enjoy looking again at that squid.  It's becoming a fishy thread.

[ollypenrice]

3 hours ago, gorann said:

Thanks Olly! I cannot wait to see what it can do with 5 - 10 more hours, but tonight is cloudy again and it is Friday which for me and the wife means fresh langustines from Gothenburg and white wine 🥂🦞

Saturday night looks promising AP wise right now

Oh, too much! I worship shellfish...

I still have three bottles of Champagne from Per's gift of a case as well... Kind of hard to drink it, though.

Olly