Image Scale - seeking advice

[Charic]

Very much still learning astro-photography, and only basic requirements here for my needs.

I have some Moon shots, prime focal, but the image scale is too small, very small. I also have some Moon shots taken AFOCAL, from a phone camera, image scale is better,  but you need a steady hand and/or a camera support.

My question......To better the image scale and to overcome the AFOCAL hand held issue, should I be further investigating Eyepiece Projection?

I'll only be using the 8" (200P) and my DSLR DX/ APS-C. Nikon D5000

I`m really only interested at present in photographing the Moon.

More to the point, who is using a similar set-up of Nikon D5000, Skyliner 8" and Eyepiece projection,. What are your findings/results?

[JED-E3]

Are you looking to do mosaics of the moon or just fill the frame? i'd have thought using your 2x barlow would allow you to fill the frame with half of the moon roughly. 

James.

[happy-kat]

Have you tried your Nikon in prime mode with a barlow?

is eyepeice projection another name for afocal?

Just read this to understand what it means

http://www.astronomysource.com/2011/10/13/eyepiece-projection/

[JamesF]

I'm confused by this, I have to say.  At prime focus with a 1200mm focal length the Moon should be pretty big on the sensor.  I'd expect it to cover at least two thirds of the height of an APS-C sensor.  You certainly shouldn't need a barlow.  With my 1500mm 127 Mak and 450D the Moon is a very tight fit at perigee.

What arrangement are you using?  Camera -> T-adaptor -> focuser?

James

[davefrance]

I'm confused by this, I have to say.  At prime focus with a 1200mm focal length the Moon should be pretty big on the sensor.  I'd expect it to cover at least two thirds of the height of an APS-C sensor.  You certainly shouldn't need a barlow.  With my 1500mm 127 Mak and 450D the Moon is a very tight fit at perigee.

What arrangement are you using?  Camera -> T-adaptor -> focuser?

James

Agree with James should be at least 2/3rds of sensor without Barlow. Are you trying to take photos of a small part of the moon?

[Charic]

JED-E3........I would have thought so too. I just want to get a larger image from the Nikon than the phone. as seen in my Gallery.

happy-kat...last night, no result

jamesF...... I would have thought a 1200mm telescope would have been better than say a 200mm Nikon lens. D5000/T-Ring/ T-Adaptor/ telescope. last night only a quick test using the Barlow, as it rained, but my thought was the Nikon sensor is too far away from focal point. I tried on Video mode (last night on Jupiter) but the image is just too small. It seems there is a lot to be gained from using a telescope lens (eyepiece projection), but someone suggested a new Barlow for me ( just sold a Revelation 2.5) and the new one has thread for adaptor, so I thought all would be ok.

Like I said in OP. Just needing a bigger image for my Nikon, on the image scale that the phone has achieved.

The Moon images in my Gallery from the DSLR is the largest scale I can achieve at present using Prime Focal. This is where I need the improvement. I like the detail of the HTC snaps, but not the blur from being hand held.

.......cant do any testing tonight due to cloud cover!

[Helite]

I have used one of the revelation projection eyepieces with my Nikon 5100 on the 200p, results were pretty good but I only used it a couple of times as I had other camera's at my disposal. Its fine for shots of the moon etc and can be barlowed too I believe to get in closer.

[Charic]

Helite......I think that's what I'm needing, a proper adaptor, wide enough to hold my BST's.

[Helite]

The revelation one is basically a 40mm eyepiece with a T-thread on top where you can mount your DSLR and snap away through the actual eyepiece, it is not compatible with other eyepieces, if that is what you mean?

[JamesF]

jamesF...... I would have thought a 1200mm telescope would have been better than say a 200mm Nikon lens. D5000/T-Ring/ T-Adaptor/ telescope. last night only a quick test using the Barlow, as it rained, but my thought was the Nikon sensor is too far away from focal point. I tried on Video mode (last night on Jupiter) but the image is just too small. It seems there is a lot to be gained from using a telescope lens (eyepiece projection), but someone suggested a new Barlow for me ( just sold a Revelation 2.5) and the new one has thread for adaptor, so I thought all would be ok.

No, there's definitely something going wrong here.  You really shouldn't need a barlow or to use eyepiece projection at that focal length.  If the image is very small then there's a problem to be found.

The size of the target on the sensor is dependent only on the focal length of the optical train.  There's no way that the image with a 200mm lens should be even remotely comparable to that from a 1200mm telescope.  The telescope should give an image six times bigger.  It's that simple.

It is possible that the camera won't reach focus, but if it won't you really can't compare image sizes.  If you can't reach focus then a barlow may help by pushing the focal plane out a bit further, but you should find that the Moon no longer fits on the sensor at all.  A projection eyepiece may well help if you can't reach focus -- my 32mm Revelation plossl has a T-thread on the back for exactly this purpose, though I've never tried it.

So I guess that's the first thing to check.  Just with the T-ring to connect the camera to the focuser, can you actually reach focus at all?

James

[JamesF]

And of course you can test for focus during the day.  Any distant target will do.

James

[davefrance]

Looking at your gallery the DSLR pics look about what you would expect from your set up. If you can get the same setup with 2 x Barlow to focus then it would still not be as big as you are wanting (from the phone pics). I think you would need to attach camera to eyepiece (AFocal) to achieve that magnification. Quality of image would depend on eyepiece, seeing, tripod/mount stability etc,

[Charic]

JamesF........( says...."The size of the target on the sensor is dependent only on the focal length of the optical train.  There's no way that the image with a 200mm lens should be even remotely comparable to that from a 1200mm telescope.  The telescope should give an image six times bigger.  It's that simple" ....// ......"So I guess that's the first thing to check.  Just with the T-ring to connect the camera to the focuser, can you actually reach focus at all?")

I totally agree. That's my dilemma at the moment. Why am I only getting the image scale portrayed in my gallery? The images (3) were with just the T-adaptors on a 1.25" tube.

 My thoughts (waiting for my new Barlow to arrive) was  that a Barlow would increase the image size somewhat?

I`ll do some daylight testing soonest

davefrance.........my understanding is that eyepiece projection is the same as AFOCAL, but the camera is fixed rather than hand held!

[houston]

Canon 1100d reachs focus with just t ring and with 2 x barlow on 200p. Im new to this but i guess moon with 2x barlow would more than fill the sensor. I unscrewed the adapter which comes with 200p and this then fits on the t ring. Some photos would be nice charic of your set up. Had same problem with eyepiece projection before with canon eos 500 film camera. Can only get the basic eyepieces to fit in the adapter but got some decent shots of the moon and planets.

[JamesF]

If we took image DSC0024 from your gallery as an example, is that the full-frame uncropped image that you got from the DSLR and 200P?

James

[JamesF]

This is the one I mean:

James

[Charic]

JamesF..........yes, bog standard image using prime focal only. I would like to get closer, as depicted in the close ups from the Android HTC pics. Although I'm happy with that shot, I`d like to get closer. That's why I thought the Barlow would allow more magnification and a tighter cropped image.

[Charic]

Canon 1100d reachs focus with just t ring and with 2 x barlow on 200p. Im new to this but i guess moon with 2x barlow would more than fill the sensor. I unscrewed the adapter which comes with 200p and this then fits on the t ring. Some photos would be nice charic of your set up. Had same problem with eyepiece projection before with canon eos 500 film camera. Can only get the basic eyepieces to fit in the adapter but got some decent shots of the moon and planets.

I'm looking at adaptors? just measured the width of my 5mm BST and its 50mm, not sure all barrels are the same width without further measurements.

[JamesF]

Ahhh, right....

Well, if that's the uncropped frame that's pretty much exactly what I'd expect to see from this combination of telescope and camera, as davefrance said earlier.  I said it should at least two-thirds fill the height of the frame and it appears to do that very nicely.

If you would like a more "zoomed in" image then you need more focal length.  I really don't think eyepiece projection would be the way to achieve that.  Ideally you should have held onto that 2.5x Revelation barlow  You can get a T-ring to 1.25" adaptor that would go into the back of the barlow which could then go in the focuser (or you can do the same thing with a T-ring to 2" adaptor in a 2" barlow).  That will give you the greater image scale you're after and I reckon it will give you much better image quality than using an eyepiece.

The Revelation barlow would probably have given you about half the Moon in a full frame.  You could add an extension behind the barlow to get even more image scale, but it may get a bit unstable.

James

[JamesF]

Thinking about it, with a 1.25" barlow you might suffer a bit from vignetting.  A 2" barlow would probably be the way to go.

James

[Charic]

JamesF........cheers. The Skywatcher 2x deluxe that I recieved this Week has the T-adaptor thread. I attach this to the T-Ring and then insert the Barlow into the Skyliners 2" to 1.25" EP adaptor. I should have seen something with that combination. Maybe the Focal planes of both camera and telescope were to far apart, but the Barlow should extend the telescopes focal plane?

Edit. I purposely decided not to get the 2" Barlow ( with a 1.25" adaptor)  after some studying, and thinking there's no need to Barlow my Panaview? 

We live and learn!

[houston]

I'm looking at adaptors? just measured the width of my 5mm BST and its 50mm, not sure all barrels are the same width without further measurements.

With an eyepiece projection adapter you will get a short focal length eyepiece to fit. Like the 10mm that came with your scope.

[JamesF]

I'd agree that you should see something with that combination.  It is probably just a question of getting the camera sensor to the focal plane.  You may well see nothing recognisable if you're too far out of focus.

It may be that you need an extension in front of the barlow to give more backfocus.  If you take the focuser from full in to full out and don't get focus then it may be worth loosening the barlow in the focuser and sliding the camera and barlow out further together to see if (and where) you get focus.  If that works then you need an extension.  Again, something to experiment with during the day.  If you need more inwards focus then that may be trickier.

James

[houston]

http://www.365astronomy.com/skywatcher-telecamera-adaptor-125317mm-p-2457.html?gclid=CMKLqPr74LwCFZMbtAodwxAAXA

[Charic]

JamesF........cheers. The Skywatcher 2x deluxe that I recieved this Week has the T-adaptor thread. I attach this to the T-Ring and then insert the Barlow into the Skyliners 2" to 1.25" EP adaptor. I should have seen something with that combination. Maybe the Focal planes of both camera and telescope were to far apart, but the Barlow should extend the telescopes focal plane?

Houston........makes sense. I thought you could use any EP from your collection.

JamesF.........I`ll check that..... At present, I only have the option to extend the camera as follows....2"Adaptor/ 1.25"Adaptor/ Barlow / T-Ring / Camera. That alone is 15cm length.

Stellarium is showing the Moon to be fairly low in the skies, so I wont see it except through the trees, although the skies are just clearing at present. Its tempting to go out, but nah! later will be fine.

So I`ll further check what i already have, and if ok, job done. If not will look into projection adaptors?