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Quatermass

Good by Bahtinov hello the Lord mask amen!

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Okey doke den.

I was only trying it because I couldn't get a reply from FLO about buying a bahtimov mask for my scope.

I'll try elsewhere for a mask then.

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Okey doke den.

I was only trying it because I couldn't get a reply from FLO about buying a bahtimov mask for my scope.

I'll try elsewhere for a mask then.

Why dont you try wrapping a bit of cardboard around the scope so its like my dew shield or a bit of old camping mat would work and then just cut out a cardboard Y shape it wont look great but if it works then who cares :)

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Your mask is on the surface interrupted by the middle part of your telescope.
I don't use [or need] a dewsheild in my obsy:rolleyes:

Could you quote reference that states the Y mask must be x inches in front of objective? and where is that measured from for a SCT? TIA

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I don't have a reference stating that the mask must be in front sorry, it just seems to me, and again I may be wrong, that if the mask is in front it cuts the light correctly and I think everyone who has tried it with SC telescope finds it wont work, well so far any way. I don't use SC telescope so can only go on what I have found using my ed80. Might be interesting to test it out again with the Y mask in front of your telescope by six inches just wrap a cardboard sheet around the end to mock up the same as having a dew shield and see if it works. Other then that I cant think what might improve things for SC telescope users.

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Thanks QM - without some explanation to precise placing I'll not experiment further. As the starlight is coming from infinity, the masks location, IMHO, can't affect results. Mask removed after I'd imaged SN2012aw last night [posted hereabouts]. I'll stick to my tried and tested method of close examination of faint stars in the downloaded fov to focus which is very sensitive. :)

Edited by nytecam

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making a bahtinov mask is a pain, .
. Not if you print it out on transparency film :-)

Best regards,

Steve

Sent from my HTC with Tapatalk

(so probably riddled with weird predicted words)

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Thanks QM - without some explanation to precise placing I'll not experiment further. As the starlight is coming from infinity, the masks location, IMHO, can't affect results. Mask removed after I'd imaged SN2012aw last night [posted hereabouts]. I'll stick to my tried and tested method of close examination of faint stars in the downloaded fov to focus which is very sensitive. :)

At the end of the night its all about what works best for you and getting good results:) everytime I change something in my set up its takes me ages to get used to it and if it doesnt work I ditch it so I know where your coming from:icon_salut:

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. Not if you print it out on transparency film :-)

Best regards,

Steve

Sent from my HTC with Tapatalk

(so probably riddled with weird predicted words)

Good idea I cut out a thin paper template and then used white car spray paint to spray through the template on to a plastic sheet but cutting out a Y shape is faster for me.:)

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I've just got a 10" dob ... ill have to dig out me old 12" singles.!

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How well does a bahtinov work on top of a wrap around dew shield? Does it matter if it's not parallel to the scope's aperture?

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Ok Crazy idea but could you arrange the legs of the secondary support cell to do this? (obviously not on a refractor :icon_salut: ) "self focusing" newtonian set up ?

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Don't think they are thick enough and if you made them thick enough, it may interfere with the image a tad.

Just my opinion though. May be wrong!

Typed using fingers, sent by me..

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Hi there Mark,

Excellent thread and tutorial. BTW.

Sorry in advance if you already have been asked but i wondered if this type mask is compatible with my 200p newt?

And as i'm new to masks and digital dso imaging, I wanted to ask you, also if any of these masks work for purely visual aids, as well - without a camera?

I always had trouble viewing not being sure 100;percent if the focus is out or in, hence the question.

Sorry if these thimgs are covered elsewhere, I did look - but still unsure.

Appreciate an experienced opinion, and of course, thank you for your time, :kiss: .

Regards

Jay

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Yes, my Bahtinov mask works just the same for visual work.

They're more often used for camera work because it can be difficult to determine if you have a true focus using the view in the LCD screen of a camera, but I must admit that on days when I'm looking at something faint I'll do a focus on a nearby bright star first before heading for my target.

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Someone asked about constructing 20 degree angles earlier. No doubt they've solved their problem by now (or given up :)) but here's an option...

http://atharvjoshi.b...ngle-using.html

That's useful - thank you :) I have a protractor so no problems with angles but that's a nice easy and accurate method :)

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I suspect that 20° isn't critical anyway - it just creates an angled gap for the central line to sit in. So 22.5° (which is not hard to get with just a ruler) "should" work just as well.

I think :)

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I suspect that 20° isn't critical anyway - it just creates an angled gap for the central line to sit in. So 22.5° (which is not hard to get with just a ruler) "should" work just as well.

I think :)

I think so too! :) Quatermass used a Y shaped twig to set his focus when he was out in the field.

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Anyone tried the mask with round holes in ,works with SCTs as the central obstruction is covered.

Just a round disc with two or three holes, two holes about a quarter of the aperture at opposite sides or three holes 120 degrees apart.

Also another wierd idea a sheet of quarter inch square wire mesh apparently gives lots of diffraction spikes.

Davey-T

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I think so too! :) Quatermass used a Y shaped twig to set his focus when he was out in the field.

Well there ya go !

Richard, wondering if Churchill's victory sign would work...?

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Bit of a "thread reserrection" here :D

Wanting a quick way to get focus for my wide field rig the other night I decided to try a quick Y mask, remembering Quatermas's twig method out in the field. These are 200mm telephoto film SLR camers lenses mounted on 1100D. I just picked up a scrap of cardboard packaging and a pair of scissors and cut out a very rough Y mask. The legs were about 8-10mm wide and I've no idea what the angle was - only that it looked like a slightly slender Y. I just popped this on the lens hood of the lens (about 30mm from objective lens I should think) and bent one leg over to stop it sliding off.

This worked very well and I got a good diffraction pattern on Auriga. That was with just lens on camera but when I tried the other camera/lens with an Ha clip filter it didn't seem to work, mainly because it was too dim. I wonder if a Bahtinov would be better but think the light would be even less.

Edited by Gina

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Hmm... yes, the light collecting area of a camera lens is much smaller than that of your telescope and adding any kind of filter would reduce that even more.

If you want to do this you could try using a ten second test exposure at a high ISO and tweak your focus between takes until you get it. This will be time consuming I should think, so it may also be worth making a note of, or marking, the focus point once you find it to make things easier next time.

Another thought would be to use the live view focussing available in Backyard EOS (it's brilliant, honest). A trial is free (30 days, so don't install it until you're sure of a good night given the lousy skies we've had for the past few months) and it's not expensive to buy. I consider this the best software/accessory that I've bought for my set up.

Edited by squeaky

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as a confirmed newtist it does make me smile that people use diffraction patterns, so often maligned by frac owners to ensure accurate focus. (now, where's that tin helmet?).

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Another thought would be to use the live view focussing available in Backyard EOS (it's brilliant, honest). A trial is free (30 days, so don't install it until you're sure of a good night given the lousy skies we've had for the past few months) and it's not expensive to buy.

If you email them letting them know you haven't been able to try the software out due to lack of good enough weather they will happily extend the trial period for you. They were happy enough to extend it for me when I mentioned it to them (they seem like reasonable people), but I never bothered in the end due to prefering to use other software.

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