first prime focus DSLR pic.. Moon surface..

[AlexN]

Hey, Just thought I'd put this up being that its my first shot at prime focus with my nikon dslr... I am lucky enough to be able to achieve focus without any modification of my OTA by the use of either my 50mm extention tube or my 4x 2" barlow.

Its a bit blurry but overall im happy for my first shot... I found shutter reflex shook the scope quite a bit so i was forced to use 1/60 - 1/80th of a sec exposures at iso400. I'd really like to be able to do a 1/15th @ iso100...

Next thing on the shopping list. EQ6 pro... that should help..

[leon]

Alex, for a very first effort with prime focus I think you have done very well indeed, :thumbsup: your should have seen my first effort :whistle:

leon :thumbsup:

This was mine 35 years ago on film :lol:

[Dennis]

Nice work Alex. Does the Nikon have a mirror lock up, or a delayed shutter release after the mirror flips up function?

Cheers

Dennis

[AlexN]

Cheers leon.

Dennis, the nikon does have delayed shutter, but i dont know about delayed after the mirror flips up... It does have mirror lock up, but i dont know if I can expose during that time... Trial and error i guess?

more to come.

[Dennis]

Hi Alex

Our Pentax had a function where the mirror would flip up and then 2 secs later the shutter would fire. Although this did reduce vibrations from mirror slap, our DSLR lunar images still suffered from blurring as the vibrations had not died down in that 2 sec period.

I would assume that if the Nikon has a mirror lock up function, you should be able to lock it up, wait for say, 10 secs, fire the shutter and then release the mirror. If it can do this, it should allow you to get nice, sharp images (seeing permitting!) at 1/15 at 100 ASA.

Cheers

Dennis

[AlexN]

After further inspection, it does have mirror lockup. Just now reading up as to whether i can fire a shot whilst its locked.. If I can, im sure I can post better images within the next few days.

:)

[iceman]

You need a much faster shutter, not slower if you can manage it.

The slower exposure will have more blurring of the features as the seeing changes.

Ideally you want 1/60+ so use a higher ISO if that helps you achieve it.

Nice first shot!

[Dennis]

Hah – I’ll bet you’re confused now, Alex!

When taking photo’s of a gibbous Moon through my F9.6 OTA, I typically use 1/50 at 100ASA and take several, oh the joys and beauty of digital SLR’s and their real time analysis on the notebook display at full resolution. When the seeing is good, I usually get a few keepers that are sharp all over, whereas the others are not quite as sharp, with some areas soft due to the variation in seeing when the shutter was released.

When capturing a crescent, I often need to go as low as ¼ sec and if I want to record the “Earthshine”, as long as 1 to 4 seconds depending on conditions.

In all cases, for my set up, mirror lock up is mandatory as I can easily see the difference, even when shooting at high ISO and 1/500 sec.

Cheers

Dennis

[edwardsdj]

Great for a first DSLR image Alex :)

On my Nikon D80, the mirror lockup feature is only for cleaning the sensor.

The exposure delay can help a bit but with my mount I find myself using a focal reducer and going for very fast (say 1/250s) exposures to limit vibrations. It takes 10s minimum for vibrations to die down for me.

[AlexN]

Mike, I know that faster, higher ISO shots will work best for the moment, but as the nikon has some noise issues at higher iso speeds, I'd like to be shooting at iso200 or lower..

Dennis, Hahh, not so much confused as determined!

Doug, Mine is a D80 also, so that rules that out... I've used delayed exposure, but an 8" dob is easily vibrated by the mirror when you're hanging the 4x barlow, 50mm extention tube, T-adapter and the camera off it... Its hardly a balanced unit.

I'll be playing with this and my toucam during the week (attempted saturn with the toucam last night, couldnt even get it in the frame????)

I've been saving all the spare coin I've got to throw at a little list of astrophotography gear that I've made up... the list does include a modded canon 40D/450D so I can use both Live View and the mirror lockup exposure mode.

[edwardsdj]

I agree: I found that keeping the ISO no higher than 400 (preferably 100) on the D80 works well for the Moon.



I'd use the D80 without any Barlow and see if you can fit in the whole Lunar disk. I found I can stack 50 or so shots like this (taken over no more than say a 1/2 hour period) to give a very pleasing result. If you can fit the whole lunar disk in, you may be able to get away with 1/250s exposures at fairly low ISO and reduce vibration and seeing effects. That's my approach to lunar imaging with the D80.

For high-resolution closeups, use the ToUcam and stack a large number of frames. Registax works well on the Moon.

[Omaroo]

You don't mention what model Nikon you have. Mirror lock-up is only for cleaning the sensor on the entry-level models.

Given that, I have both a Nikon D40 and Canon 350D. Without mirror lock-up set on the 350D it slaps its mirror much harder than the Nikon when it fires - and you can feel it when it does so, whereas you can't on the Nikon.

[AlexN]

Chris,

I have both a D50 and a D80. The D80 was used...

[Omaroo]

The 0.4 sec exposure delay should be heaps if your mount is solid I would have thought. The Canon only gives their users slightly more.

[AlexN]

I have not yet figured out how to use the exposure delay apart from the 10sec countdown timer... (only got the D80 recently...) If you can point me in the right direction I'd be a very happy young lad!

[Omaroo]

Sure Alex. The countdown timer is different again. It waits 2,5,10 or 20 (if I recall) seconds after you hitting the shutter button before releasing the shutter - but that's all. The Canon 350D only has 10 secs as an option, which is way too long and unconfigurable. The shutter still opens only just before the shutter curtain opens. The D80's exposure delay pre-swings the mirror up and then waits 0.4 secs until the shutter fires. The damping, as I've said before, is more subtle than a Canon's, so 0.4 secs should be enough time if your mount is halfway stable. I'm unsure as to whether or not you can tie the two functions together - i.e. have a shutter count down delay of, say, 10 seconds that lets you hit the button which starts it counting. At the conclusion of that count it'd be nice to flip the mirror via the exposure delay and have it all settle for 0.4 secs before finally opening the curtain.

Its found in Custom Menu 31 - "Exposure Delay Mode" which introduces a 0.4 sec delay to shutter-release in order to reduce camera shake (macro, telescope, microscope photography).

31: Exp. delay mode

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[AlexN]

Cheers Chris, Hopefully it makes all the difference.

[Dennis]

FWIW, I have noticed that even the 2 sec delay on my Pentax *ist DS is an insufficient time delay for the mirror slap vibrations to die down to the extent that image quality does not suffer. One night, I performed some ad hoc tests on bright stars which consistently showed “double stars” or signs of smearing and found that I was only able to obtain non-vibration affected shots using a minimum of 10 secs as a delay (by covering the front of the OTA and counting 1001, 1002, 1003….etc).

I haven’t tried the same (rough) experiment using our Canon 40D as it does have a genuine mirror lock up. Even though the 40D has a less mechanically violent mirror up/mirror down action than the Pentax, with both up/down actions controlled by some form of piston rather than spring, I still use MLU on the Canon.

Cheers

Dennis