What would you shoot with a 0.7m RC at 8400mm FL?

[Datalord]

I'm curious what could be good targets for these huge systems if they are used for pretty pictures? 

[vlaiv]

Depends on sensor used.

Any decently sized sensor paired with such scope will easily have nice FOV to frame galaxies or planetary nebulae for example.

[Neil_104]

My first target would be a pretty bl**dy good guiding solution at that FL!

But jokes aside, I'd aim for smaller targets so I could frame them nicely with some background space/stars. With a smaller sensor that could only just cover the object, it could also be fun really zooming in on some well-known objects like, say M13, and would give some unusual and new perspectives of familiar objects.

Edited January 28, 2023 by Neil_104

[The Lazy Astronomer]

Second the above: planetary nebula or galaxies that are normally out of reach for most amateurs to image with a good level of detail. 

[ONIKKINEN]

Coupled with one of these: https://www.qhyccd.com/scientific-camera-qhy6060/

It could shoot any of the usual targets with plenty of room to spare. I would image one of the common galaxy targets to see how much more 0.7m aperture would show compared to normal sized scopes, so something like M51, M81, M101. The GSENSE6060 sensor cameras cost about as much as a house, but if i could afford a 0.7m scope and a place to mount it im sure its just another accessory at that point.

[ollypenrice]

There is such an instrument down the road from me but it isn't used for imaging. If invited to use it (a big 'if') I think I'd try the Cat's Eye nebula.

Olly

[DaveS]

Well, I wouldn't want to *shoot* anything, but I might try imaging some of the smaller HCGs. Stephan's Quintet might be high on my list.

[Datalord]

Yeah, everyone going for galaxies makes a ton of sense. I have a love for the ARP catalogue, so lots to spend time on there. 🤔

[DaveS]

Here we go, Copeland's Septet in your 0.7M dia, 8.4M fl 'scope

Edited January 29, 2023 by DaveS
Formatting

[Datalord]

1 hour ago, DaveS said:

Here we go, Copeland's Septet in your 0.7M dia, 8.4M fl 'scope

Damn, still looks small. I don't know that one, what's the size of it? 

[DaveS]

OK, this is the sky view. It's just above Leo's backside

And the FoV in my ODK 12 / G3 16200 ( A fair sized 'scope by amateur standards)

 

[Datalord]

Hmm, I'm actually surprised. I also have my 12" 2.4m RC, but I thought having a much larger scope like that would make more of a difference. Obviously acquisition time "should" be faster, with all the caveats of camera etc, but I really thought a tripple in FL would be bigger. 

On the flipside, that means a lot of the usual targets are still viable. 

[ollypenrice]

3 hours ago, Datalord said:

Hmm, I'm actually surprised. I also have my 12" 2.4m RC, but I thought having a much larger scope like that would make more of a difference. Obviously acquisition time "should" be faster, with all the caveats of camera etc, but I really thought a tripple in FL would be bigger. 

On the flipside, that means a lot of the usual targets are still viable. 

More focal length projects a larger image onto the chip. This much we know. Does this larger projected image contain more resolved detail than a smaller image? This we do not know, because it depends on your seeing.

Larger aperture collects more light. This much we know. Does this increase in light collection increase the amount of light per pixel? This we do not know, because we don't know your pixel size.

Larger aperture, in a diffraction limited optic, resolves more detail. This much we know. Is this increase in resolution sustained by the seeing? This we do not know.

That makes for a lot of unknowns, two of them coming down to the seeing. 

Olly

[vlaiv]

59 minutes ago, ollypenrice said:

More focal length projects a larger image onto the chip. This much we know. Does this larger projected image contain more resolved detail than a smaller image? This we do not know, because it depends on your seeing.

Larger aperture collects more light. This much we know. Does this increase in light collection increase the amount of light per pixel? This we do not know, because we don't know your pixel size.

Larger aperture, in a diffraction limited optic, resolves more detail. This much we know. Is this increase in resolution sustained by the seeing? This we do not know.

That makes for a lot of unknowns, two of them coming down to the seeing. 

Olly

We do know one important bit related to seeing.

In the same seeing, larger aperture will resolve more than smaller aperture.

How much more, that I agree, we don't know , but we do know that it will resolve more, regardless of how poor seeing is - if its the same for both scopes.

[Datalord]

Adding fuel to the fire, what cameras are even available for such a monster? I saw the qhy6060 with an 80mm 10*10 sensor mentioned in the thread, but any other available? 

[ONIKKINEN]

There are also the IMX461 based medium format cameras, or the GSENSE4040 based ones, both around 50mm+ diagonal. Still costs about as much as a decent car, but nothing compared to the 700mm RC so almost a good deal at 10k£ (at least).

[DaveS]

This is the FoV with the Gsense 4040 on the 0.7M RC, again using Copeland's Septet as a reference

And just to show that you don't need a big RC to get a narrow FoV, just need to be totally barking. My ODK 12 with my SX Trius 694

[Datalord]

2 hours ago, ONIKKINEN said:

There are also the IMX461 based medium format cameras, or the GSENSE4040 based ones, both around 50mm+ diagonal. Still costs about as much as a decent car, but nothing compared to the 700mm RC so almost a good deal at 10k£ (at least).

Yeah, I looked at qhy for their cameras. Honestly, the 411 based cmos at 150mp looks like an amazing camera. Binned 2x2 it gives a full well of 320k and a huge sensor. Btw, the 0.7m scopes come in at $200k+, so the cameras are a drop in the ocean to compare. 

2 hours ago, DaveS said:

This is the FoV with the Gsense 4040 on the 0.7M RC, again using Copeland's Septet as a reference

This actually looks very good. 🤔

2 hours ago, DaveS said:

And just to show that you don't need a big RC to get a narrow FoV, just need to be totally barking. My ODK 12 with my SX Trius 694

And yes, that would indeed be barking mad. Seems like you would just waste a whole lot of telescope.