Which camera/filters are best for Bortle 1 Skies? - Forums

Topic starter

Jun 1, 2024

Luckily I was able to get a pier in a new remote observatory near my home (2 hours) in B1 skies.

I purchased an Esprit 100ED refractor to send there and now I'm trying to decide if my IMX571 color camera (has UV/IR Cut window) + 3.5nm OIII/Ha and 4 nm OIII/SI dual-narrow band filters are the best equipment to send.

I've heard rumor's that Monochrome can give better results in light-polluted skies like I have at home (B7) but I'm not sure if that's true for B1 skies too??

For narrowband, is there any point to super narrow filters like Antlia 2.5nm set at such a dark sky site? Would cheaper 5nm, 7nm, 10nm, or even 12nm filters work just as well? It seems that 7nm or 10nm would be better for OIII (covering both emission lines: 495.9, 500.7), and for Ha (covering Ha: 656.3 and both NII lines: 654.8, 658.4), but can 3nm can cover both SII lines (671.6, 673.1) if it's centered properly (any reason to use 5nm or 7nm filters for SII)?

For broadband would Mono be any better than bayer-drizzled OSC in B1 skies?

I'm going to have to purchase another camera (either mono IMX571 or another color IMX571) to either send to the remote site or to keep at home after sending my existing color camera to the dark site. Another color camera would be significantly cheaper than a mono camera plus 7 filters. (I'll need a filter wheel for either camera so that cost doesn't factor in).

So I'm looking for guidance for what work best from a B1 sky.

Thanks for all your forth coming suggestions.

Tommi Liinalampi

Jun 1, 2024

I live under bortle 3 sky so I can speak about my own experiences and thoughts.

If you want to take full advantage of dark skies you should swamp read noise of your camera. It's quite easy in cities, but you should think more under dark skies. Especially when take photos with very narrow bandpass like 3nm.

I have also Esprit 100ED (now reduced to F/4.1) and FRA 400 (F/3.9). I use ASI294MM which have larger pixels (4.63um) to get more electrons to one pixel. However, when I use Antlia 3nm filters I need even 900 seconds to swamp read noise (about 8-10x times). For me it's not meaningful to use much longer exposures than this, so if you use slower systems I would choose larger bandpass than 3nm.

IMX571 has smaller pixels but same time lower read noise than IMX492 (ASI294MM) so optimal exposure time might be about same. But if you use Esprit 100ED with native focal length instead of F/4.1, it doubles your exposure times. Then you may need 30 minute exposure times or even more when using 3nm filters. And then your mount should be very stable and accurate.

Helpful

John C. Yu

Jun 1, 2024

For B1 sky, 16Bit mono cam with filters will be the best choice. Filters like Chroma, Antlia Dark series are good choice.
John

andrea tasselli

Frequent contributor

Jun 1, 2024

Anything works in B1 skies, even your own eyeballs! For me it would be a no brainer to go for a color camera and dual-band or tri-band filters. 7nm band-pass should suffice even with high moon.

Gilmour Dickson

Jun 1, 2024

I am interested in the answers here as I live under B1 and am contemplating a camera upgrade. From a 533mc to either a 533 mono or IMX571 colour or maybe mono. If you are going to the effort of remote I can't help but think that mono will give you more options and flexibility and overall just better and cleaner data. I am regularly imaging with also two dual band filters and it is good fun, but I can't help but feel that full mono is a better option.

John Stone

Topic starter

Jun 2, 2024

Thanks for the answers so far. I'm hoping there will be other opinions as well.

Well Written Respectful

Oscar

Jun 2, 2024

If I were you, I would use Mono

You'll get more data in less time with Mono

Plus, it seems easier to process

Arun H

Frequent contributor

Jun 2, 2024

John Stone:
I've heard rumor's that Monochrome can give better results in light-polluted skies like I have at home (B7) but I'm not sure if that's true for B1 skies too??

The advantage of mono in light polluted sites is that each color is not affected by light pollution outside of its wavelength band, whereas the broader bandpasses of color cameras mean a greater impact from light pollution and complex gradients that need to be managed.

Frankly, if I was imaging RGB from a B1 site, I'd go with a color camera. Color data will be rich, you'll always have a "complete" set of subs. Nominally, a mono might capture more signal in a given amount of time. It is hard to estimate exactly how much, but rough numbers are 20% greater SNR in the same time in theory, though because of the way LRGB combination works, I expect in practice, it will be less than that. You can use a dual NB filter to get narrow band data, but if budget was no concern, I'd personally use mono. I fully expect that a 5 nm filter set should be sufficient from such a site, perhaps even 7nm. I would place a premium for peak transmission of the filters in this situation over the bandwidth, i.e., I'd select a 5 nm filter with 95%+ peak transmission over a 2.5nm filter with <90% peak transmission. The amount of desired light you are letting in becomes more important than rejecting undesired light in areas with absence of light pollution.

Helpful

JohnHen

IOTD Staff

Jun 2, 2024

Arun H:
if I was imaging RGB from a B1 site, I'd go with a color camera.

I fully agree. Not from my own experience (I haven't imaged from a B1 site yet) but from what i have seen from imagers who occasionally image from B1 locations with OSC, for example @Christoph Lichtblau with this image https://www.astrobin.com/full/mqqpad/0/ or this this https://www.astrobin.com/full/xpx1t1/0/ and several others.

Gilmour Dickson

Jun 3, 2024

Arun H:
if I was imaging RGB from a B1 site, I'd go with a color camera.

I fully agree. Not from my own experience (I haven't imaged from a B1 site yet) but from what i have seen from imagers who occasionally image from B1 locations with OSC, for example @Christoph Lichtblau with this image https://www.astrobin.com/full/mqqpad/0/ or this this https://www.astrobin.com/full/xpx1t1/0/ and several others.

I see it as target dependant. I could decide to upgrade to a 2600mc (from my 533) and if I was imaging only dark and reflection nebula and galaxies then I would be just fine. But then comes emission nebula where dual band filters can work really well or sometimes not. With mono there are no compromises. Your Oiii is not going to be overwhelmed on certain targets because if you want to can shoot as much Oii as you want. And if you want RGB then it is there in the filter wheel. If you want to shoot Ha on a full moon you can do so. Just flexibility.

OSC I can totally get for a trip out to dark skies where you want to come home from the trip with a finished image. But for a permanent mount with the complexity and nature of it all I would go mono for sure. It just gives more options and better data (how much better is a whole discussion of course, but I don't think anyone can dispute there is a gap).

Arun said he would go OSC for RGB, but to be clear he then went on to say that; " but if budget was no concern, I'd personally use mono".

Helpful Insightful Respectful Engaging