Skymax 127 Webcam Focus

[DeepThought]

Hi

Does anyone here use a Skywatcher 127mm maksutov with a webcam attached?

I had a go with my modified Xbox camera last night but just couldn't find focus with it. Given that the secondary mirror focuses to such a long focal length, I think the camera sensor was just too close to the secondary to even get close.

If anyone here has managed this, could you give me an idea how far away from the secondary you had to mount it to achieve focus?

Many Thanks

[chiltonstar]

Hi

Does anyone here use a Skywatcher 127mm maksutov with a webcam attached?

I had a go with my modified Xbox camera last night but just couldn't find focus with it. Given that the secondary mirror focuses to such a long focal length, I think the camera sensor was just too close to the secondary to even get close.

If anyone here has managed this, could you give me an idea how far away from the secondary you had to mount it to achieve focus?

Many Thanks

I have no problem finding focus (Mak 127, barlow) - I just leave the diagonal in place and pop the webcam nosepiece in after removing the EP. I then have to focus back a bit (eg on the Moon or something obvious) to get sharp focus. You have removed the webcam lens?Chris

[JamesF]

Does anyone here use a Skywatcher 127mm maksutov with a webcam attached?

In a Churchill dog style... "Oh, yes!"

I had a go with my modified Xbox camera last night but just couldn't find focus with it. Given that the secondary mirror focuses to such a long focal length, I think the camera sensor was just too close to the secondary to even get close.

If anyone here has managed this, could you give me an idea how far away from the secondary you had to mount it to achieve focus?

One of the unexpected but entirely logical behaviours of a Mak-Cass is that the focal point moves as the primary moves, which means (within reason) you can get it to focus nearly anywhere. I've used my DSLR with a T-ring straight on the visual back and with a 50mm extension. I can get focus in both positions without trouble.

I've used an SPC900, Xbox cam, modded Lifecam, ASI120 and probably others in my 127 Mak, and they all work fine. I put the camera straight into the visual back, without the diagonal. They'll focus with the diagonal as well, but it's just another bit of kit to get in the way when you're imaging. It does sometimes seem like you have to wind the focuser forever though. It's something like 22 or 23 turns end-to-end. I'd suggest pointing the scope at something a good distance away during the day and focusing on that to find out roughly where you should be and how much diffefrence there is between that and whatever eyepieces you intend to use.

Also be aware that it's really easy to think you have the target centred in an eyepiece, but to have it completely miss the camera sensor because it's so small. There are cheap 12.5mm illuminated reticle eyepieces around. They're not stunning quality, but they do the job and allow you to get the target dead centre (I don't actually bother focusing to use mine as long as the defocused image is centred).

James

[DeepThought]

Excellent replies, thank you.

I'm probably just not being brave enough with the focus, stupid as it sounds I always worry that I'm going to overwind it and do some damage.

I'll have a play with a terrestrial object tomorrow.

Many Thanks.

[JamesF]

I'm probably just not being brave enough with the focus, stupid as it sounds I always worry that I'm going to overwind it and do some damage.

You can't "overwind" it really. Not unless you get fairly violent with it to do so, at least. You'd probably have to get a pair of pliers on the focuser knob or something The knob turns a threaded rod that pushes and pulls the mirror carriage back and forth. It quite clearly stops at either end of the travel before anything untoward happens.

James

[JamesF]

Actually, if you want to see what it looks like, here's a photo:

http://www.tanstaafl.co.uk/wp-content/uploads/2012/02/IMG_0068.jpg

James

[knobby]

And all those o rings...

[DeepThought]

Just to square off this thread, I finally got the webcom to focus by using it with the supplied barlow lens with the optics unscrewed from it, effectively acting as a short extension tube.

Who knows, maybe someone will stumble upon this thread in years to come and thank me for this.

Now all I need is some clear skies and something to point it at.

[JamesF]

It won't be too long until Mars and Jupiter are about earlier in the night and there's always the Moon. Meantime, globular clusters might be viable targets with the DSLR and a T-ring?

James

[coppernob]

Hi,

here are my images tonight using my Mak 127 and my neximage 1 on the moon without a barlow. A bit green as I havent altered the colour balance. Cannot wait to try on Jupiter. Focussing can be a challenge through the camera which is a modified And rebadged spc900 but is roughly parfocal with my 10mm plossl eyepiece.

Sent from my iPad using Tapatalk HD

[JamesF]

It really is made of green cheese!

They're good images, even if the colour is a little odd.

Focusing with the Mak is a little tricky. When you change the direction of travel the primary mirror rocks slightly which shifts the image without changing the focus and then it starts to change, which means you can't move the focuser too far and then move back by the same amount to get back to where you were. Unfortunately there's little that can be done about that. I bodged a motorised focuser onto mine and that made a world of difference to imaging.

James

[Drubug]

Hello all,

My first post joining here and already have a question....

I also have a Mak127 and have got a old webcam which I have stripped out the autofocus lens so just have the CMOS sensor showing.

Now when I mount it onto the telescope, after taking out the EP. I can focus it with a bit of adjustment, but I am only focusing in on a small section of the image. Massive amounts of magnification in a sense, as the webcam is only seeing a tiny square of the image coming through.

Is this expected or have i got something terribly wrong... I reckon i am seeing a focused image of about 5-10% of the actual full image in the telescope.  ???

[JamesF]

Is this image of the Moon, by any chance?

At the focal plane of the 127 Mak without a barlow the image of the Moon is about 15mm diameter, so if the camera sensor is considerably smaller than that then I'd only expect you to see a small amount of it.

James

[JamesF]

Oh, and welcome to SGL

James

[Drubug]

James, thanks for the advice.... Not even pointed it skywards yet... This was on a building about 2 miles away out my window... So the fact I can only see 1 window of the building 2 miles away makes perfect sense!!!

Least I know im not doing something "totally" stupid. Now I can play around and see what works best.

And thanks, exicitng as only got telescope last night!

Looks like I might get first view this evening is blue sky stays that way!

[JamesF]

Yup, that sounds about right.

Since I mentioned the Moon, if you're interested in full-disc images of the Moon and have a DSLR then putting it straight onto the back of the 127 works very nicely.  The planets by comparison are tiny.  Without a barlow even Jupiter will appear quite small on your camera sensor -- it should be around 1/3rd of one millimetre across at the focal plane.

James

[Drubug]

Useful to know. 

Once I had a play will get some different EP's and Barlows. 

Think I will pick up an old DSLR, there are some good bargins on ebay...

[JamesF]

Canon models are often considered best as there's software to control them from a PC, though I think once you get older than the 450D models they don't tend to be supported so much, either in third party software or even in Canon's own.

James

[Mick J]

Think I will pick up an old DSLR, there are some good bargins on ebay...

Welcome Drubug, ebay, gumtree and there are a couple of 450D's on abs just now, canon's work well for astro, lots of software available to play with.

[Drubug]

Again thanks for the advice. I had read that Cannon was the best option... May have to wait till Jan, might be some better bargins. plus the bank manager might not have such a heart attack. Already bought telescope this month!!