Super Impressed with the ZWO 2600MC Pro on the RASA 8 (single 4min sub at 2xbin)

[Catanonia]

For once, new kit arrives and I have a few hours clear skies to try it out   I must have done something good this week

So replacing the ZWO 183MC Pro with the ZWO 2600MC Pro as I want that large FOV

The 2600 has almost twice the fov with the APC sensor size.

• Zero amp glow compared to the 183
• Only slightly bigger pixel sizes
• Large x by y resolution
• Much deeper wells to capture those photons
• And is twice as expensive

 

So here is 1 single sub from the RASA 8 and the ZWO 2600 MC Pro

• Single Sub at 4minutes guided and 2xbin
• No Darks, Bias or Flats applied
• lEnhance 2inch filter
• Gain 100 on the 2600 and -10 temp
• No processing other than a stretch, image horizontal flip (as RASA images in reverse due to camera on the front of the scope) and convert to JPG to make it visible on the forum
• Taken from less than impressive Bortle 6 skies and not even properly dark yet.

This is almost as good in a single sub as my pictures before I left the hobby 7 years ago. How much tech has changed.

I am very impressed and the images are rolling in now.

Edited September 14, 2021 by Catanonia

[paul mc c]

Can't seem to see it. 

[Catanonia]

Just now, paul mc c said:

Can't seem to see it. 

edited the post

 

[paul mc c]

Brilliant.. 

[michael.h.f.wilkinson]

Stunning, especially for a single sub

[ollypenrice]

Like you, I'm knocked out by this combination.

Interesting that you're at 100 gain. We've yet to try that.

Olly

[gorann]

6 minutes ago, ollypenrice said:

Like you, I'm knocked out by this combination.

Interesting that you're at 100 gain. We've yet to try that.

Olly

Yes it is a truely great camera! I allways run mine at gain 100 and offset 30. Gain 0 works fine too  but after an initial comparison I thought subjectively that gain 100 gave a slightly better result (but at the cost of more subs to handle)

[Adam J]

Very impressive in terms of signal from such a short exposure. The thing that has put me off a RASA though is the spot diagrams which show spots of 8um or more at the centre of the FOV, hence not too sharp for such a large aperture. Can you or Olly or Gorann maybe comment on sharpness in comparison to some of the optically slower alternatives?

I do note that this is 2xbin though. 

Adam 

Edited September 15, 2021 by Adam J

[ollypenrice]

1 minute ago, Adam J said:

Very impressive in terms of signal from such a short exposure. The thing that has put me off a RASA though is the spot diagrams which show spots of 8um or more at the centre of the FOV, hence not too sharp for such a large aperture. Can you or Olly maybe comment on sharpness in comparison to some of the optically slower alternatives?

Adam 

I think your reservations may be justified. My impression, though I need more experience with the setup to be sure, is that a sampling rate of 1.8 arcsecs per pixel is not going to support presentation of images at 100%. A refractor of comparable focal length would be better in that respect. The question is, though, 'Does it matter?' That depends on your imaging objectives. I don't regard a FL of 400mm as one with which I'll go looking for the finest details. It's a widefield FL and, in widefield imaging, I find most of the interest lies in going deeper rather than in finding small-scale details. Obviously the RASA is at its best in that rôle. And, even at 50% of full size (which it certainly does support), the result is crisp and clean in most respects. A soft extended glow around bright stars is a RASA characteristic just as diffraction spikes characterize spider vane reflectors. 

All optics involve compromise and we choose the compromise which best suits our purposes. If our aim is to find faint, large scale structures which are rarely imaged, the RASA might be the right compromise. If the aim is to make large scale mosaics in which downsizing of individual panels is something we're going to do anyway, then the 'resolution compromise' disappears entirely.

It's also likely to be the right compromise for the imager exasperated by bad weather and lack of integration time.

Whether or not the RASA is right for you depends on what you would like to do with it.

Olly

 

[gorann]

I fully agree with Olly. The job for a RASA (or other short FL low f-ratio scopes like the Epsilons) is not go show fine detail in distant galaxies. When viewed at the right image scale (up to A3 I would say) the images are crisp. What I have done on occation is to supplement the image with higher resolution data from my longer FL scopes. A great thing with the RASA is that seeing is almost never too bad for it. At nights when bad seeing gives me a guiding RMS around 1.5"/pix the RASA images still look great while imaging with anything above 1000 mm FL becomes rather useless.

[Catanonia]

4 hours ago, ollypenrice said:

Like you, I'm knocked out by this combination.

Interesting that you're at 100 gain. We've yet to try that.

Olly

Yeah, a lot of forum searching showed this to be the most recommended gain setting of 100 due to the extra high mode the camera goes into. As long as you don't completely fill the wells, it is ok I guess. Hard to do with such deep wells even 4mins at 2xbin.

I am using the ASI Air Pro and so I can't play with the offset.

Creating the final image now with 20x good subs I got last night and will post soon.

[Catanonia]

5 hours ago, Adam J said:

Very impressive in terms of signal from such a short exposure. The thing that has put me off a RASA though is the spot diagrams which show spots of 8um or more at the centre of the FOV, hence not too sharp for such a large aperture. Can you or Olly or Gorann maybe comment on sharpness in comparison to some of the optically slower alternatives?

I do note that this is 2xbin though. 

Adam 

I am still learning this scope and camera combination. But I would also agree with Olly, this scope is not for close in detailed work. It is all about the "bigger" picture.

I still have the 183MC Pro that I can use if I want even smaller pixel sizes, but to be honest that is probably wasted on the RASA8 as the FL of 400 generically means I will not be getting in close to galaxies or the like and with the 183MC, all I am really doing is sacrificing FOV in the final image.

Edited September 15, 2021 by Catanonia

[Chris]

This is brilliant! Super clean for a single stretched sub, and that detail can't be from a light stretch....or maybe actually with the RASA. 

[Catanonia]

13 minutes ago, Chris said:

This is brilliant! Super clean for a single stretched sub, and that detail can't be from a light stretch....or maybe actually with the RASA. 

You will have to trust me, this was only histogram stretched and converted to JPG.

This is the RASA 8 @F2 at work here as a light bucket. The great noise is down to the ZWO2600MC Pro at gain 100.

[Davey-T]

7 hours ago, ollypenrice said:

Interesting that you're at 100 gain. We've yet to try that.

Only ever used mine at 100 gain as recommended by someone, can't remember who but not enough clear skies here to do experiments 😂

Dave