LUNA 5-29-20 Sometimes It's The Tool You Use

[Hankmeister3]

Sometimes it's the tool you use … or don't use. A near first quarter moon was up and my main mission that night was to acquire more DSO frames to toy around with in PhotoStudio 6.0. I noted Luna riding proud in the sky near the meridian and wanting to kill some time (four hours!) I made Luna the first target for the evening. I even bothered in the first place because I noted through my camera's LCD display screen the atmosphere was relatively steady even at that first hour after the sun set. Thermals were still roiling off the asphalt roadway about 100 yards away but I was still looking at about a Pickering 5+ sky.

The Quattro 8 f/4 is a very fine instrument for relatively short exposure times when capturing DSOs. It's ability to gather lots of photons and concentrating them on a DSLR CCD is practically unparalleled except by another f/4 optical train. Since I'm generally a single-frame astrophotoger, a "fast" optical system is good and faster is better. I'm not sure if there are any moderately priced f/3.5 or f/3 tube assemblies out there but anything in the f/4 to f/6 range - reflector or refractor - is putting a lot of photons on a relatively small patch of any imaging device - digital or film-based. It's how photo-imaging works at its most fundamental level, the lower the f-ratio/number, the more light it delivers to the image plane within the camera. There's a lot of other optical mumbo-jumbo I could pass along, but I'd either be preaching to the choir or … I'll just spare you for now! It is a very fascinating subject.

Suffice it to say that I would have preferred using my Meade 10-inch f/10 because of its much larger image scale at prime focus and also with eyepiece projection, and it doesn't suffer as much field curvature or coma as faster optical systems, except for maybe the Ritchey-Chretien family of telescopes. Also the resolving power of a ten-inch piece of main objective glass plays some role in producing "sharper", more detailed planetary and lunar photos. And higher resolving power is useful for resolving really close binaries and triplets, though atmospheric conditions often muck up that advantage.

I did forget to switch my Canon 80D camera over to monochrome mode so these are "full-color" images - well, as much color as mistress Luna is able to deliver. Exposure times were between 1/150 and1/200 seconds at ISO 100 at prime focus. The bottom photo is simply a 2X crop of the same 20 stack image. DSS chose 20 out of the 40 images I fed it to stack and I thought the final result was worth posting here to demonstrate that sometimes when you have the wrong tool in your back-pocket, you can still get some decent results.

[Graeme1858]

Looks like the Quattro did ok to me!

Regards

Graeme

[Hankmeister3]

Thanks, Graeme. Right now, when it comes to lunar photography, I feel like I'm taking two steps forward and one step back. The Quattro fast Newtonian simply isn't the right scope to use given its relatively small image scale and the huge secondary which is a real contrast killer.