Unable To Focus On The Moon

[G2EWS]

Hi All,

I mentioned in my first account of setting my scope up yesterday that after looking at the moon I decided to try and take a photo.

I put the camera on the end in place of the eyepiece in exactly the same way as I did the day before with Peter - S.A.M and no matter what I did I could not focus on the moon.

I tried both the Nikon D3X and the D3S, had them on live view, even zoomed in on the view finder.

All I could see was a bright blurry blob.

Just wondering if there is something I was obviously doing wrong.

Just going to see if I can focus down the garden again before going to the office.

Best regards

Chris

[G2EWS]

OK, I just tried again in the house looking down the garden and beyond and I appear to be able to focus.

However there is such a large change in the focal length over about 100M that I am wondering if I just cannot get the correct length with the moon. In the garden the adjustment is almost fully out. About 150M away it is turned a long way in.

So over to you experienced astro photographers. I have my focal reducer and obviously Nikon adaptor.

Best regards

Chris

[jgs001]

Chris, remind us what scope you are using ? With my 80ED, I've used it for the moon, and birding, down to really quite close, but I need a 50mm extension tube to reach focus.

[Ant]

It sounds to me like John is right... You need an extension tube.

If you have a 2" diagonal, you can use that to test and make sure it comes to focus OK - then buy a extension tube.

Cheers

Ant

[G2EWS]

Hi John and Ant,

Thanks for responding to my cry for help!

I have the 80ED as well.

So what you are saying is that as well as the reducer I will need an extension tube?

I am sure someone mentioned that but I thought the reducer would do that. Right I will add that to the order for some eyepieces right now!

Best regards

Chris

[G2EWS]

Just put what I have on a signature so others don't need to wonder in future. Hopefully I have done it correctly.

Regards

Chris

[themos]

The further something is, the closer in does it come to focus. If you're having trouble with the moon but can focus at objects 150 metres away, your problem is not enough inward travel of the focuser. With the focuser all the way in, what how far is the most distant object you can focus on?

[G2EWS]

Hi Themos,

That is a good question I will have to check when I get home.

What you are saying is I need the opposite of an extension tube! Hmm!

Best regards

Chris

[themos]

If the moon looks bright and blurry, it could be that you're simply overexposing (as opposed to not being in focus). Adjust your camera manual settings to bring down the intensity of the image: expose for shorter time (maybe 1/100 second) and close the diaphragm (maybe f/8). Also, use "daylight" level ISO, maybe 200?

[G2EWS]

Hi Themos,

Interesting point and I will have a play next time. But surely if I am looking at live view it should still be in focus. Obviously I would adjust accordingly to 'get' the photo, but on live view, all should, I would have thought been clear once I focused the scope?

Best regards

Chris

[themos]

Not familiar with Nikon's LiveView so it could well be that it doesn't do Automatic Exposure adjustment depending on what mode you've put the camera on. I remember a few weeks ago using someone's Nikon + lens to take a handlheld pic of the Moon and LiveView was giving me a very over-exposed blurry moon until I changed the exposure parameters.

[jgs001]

Chris, everything I've heard indicates that using the FF/FR, when attached, means you don't need the extension tube. For the moon, ISO100 is fine... at the current phase, at f/7.5... you'll be looking at something like 1/200s I'd think...

[Simms]

Actually the poster above you got this right. Even as a professional photographer I failed to expose the moon as one would a day time object (if using spot or center weighted focusing) and my first few attempts were so overexposed that the moon seemed out of focus - but after dialling down the ISO and upping the shutter speed it all fell into place - not sure about your Nikons but my Canon simulates the exposure in Liveview, its not perfect, but allows me to eye in the settings before finetuning with 2 or 3 test shots - I`d assume your Nikons would do this as they are top-end bodies. Good luck!

[G2EWS]

Hi Themos, John and Simms,

Many thanks for the response.

The auto focus is not going to be relevant without using one of my Nikon lenses, so it is obviously going to be manual and on the scope.

It is interesting about the over exposing and I cannot remember checking the ISO settings. If as Simms suggests the live view is simulating exposure and giving it some thought I think it does then indeed that may be the problem.

Funny how we own these things but don't always understand all the settings! I almost never use live view due to using a seriously good tripod and will always take a lot of time getting the photo 'right'. However I am aware that it can be a good idea to use it due to the fact that you can zoom in to make sure the focus is correct on a macro shot where manual focus is the order of the day!

Bet there is no moon tonight for me to have a play!

Best regards

Chris

[Simms]

Liveview is a godsend for macro photography, and I am finding its just as valuable for Astro photography - although the best thing about Astro photography is that the stars/planets/nebula are not going anywhere in the near future so if you fluff a few shots one night, you always have plenty of more chances to get it right... Now weddings on the other hand..

[G2EWS]

Liveview is a godsend for macro photography, and I am finding its just as valuable for Astro photography - although the best thing about Astro photography is that the stars/planets/nebula are not going anywhere in the near future so if you fluff a few shots one night, you always have plenty of more chances to get it right... Now weddings on the other hand..

Hi Simms,

Got to agree with live view for Astro photography. Cannot see an easy way without it.

As to weddings, now making a mess up there would be problem. Been offered to go to India to do photos of a wedding over 4 days

Regards

Chris

[CKemu]

Live view on Nikons auto adjusts its exposure to compensate, though it is a bit tetchy with the Moon as its a veey high contrast object. As a studio and street photographer I consider live view a plague upon mankind, and always chuckle at people with tripods and liveview enabled to take the simplest of shots!

However until I get an off-axis view finder, it will have to do for astrophotography, I really do not enjoy the glare from the screen!

Back on subject, I can comfortably photograph a full Moon at ISO 200 @1/160 - 1/250 and sometimes go for 1/320 if I want something a bit more moody!

The Moon currently is about ISO400-640 @ 1/100 - 1/160, though mileage will vary.

If you look through the eyepiece and it seems out of focus, then you might consider a Crayford focuser to attach? Not sure, photography I have years of experience with, but astronomy is a new field fof me, but with a Crayford you get more subtle control and it moves the fcousing plains further apart - which works afaik like an extension tube.

Over-exposure would create a sharp fall-off and an in focus white disc, soft focus would lead to a smoother fall-off and a hazy white disc to.

Oh and dam you for having a D3x! My D300 feels slightly sad!

[jgs001]

You should be able to get a rough focus through the viewfinder, and then use liveview for critical focus. That way, you'll know that you're about there, and if the liveview appears way out, it's defo the exposure. You really don't ever need to use an ISO higher than 100 for a decently mounted lens/scope. I regularly shoot with my C80ED and a 2xTC (f/15) at ISO100 and 1/15s on the moon, during the slim crescent of course, but no problems with that.