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Hi Folks,

not sure if this should be here or in imaging but here goes..

Trying out my spc900 and 130p tonight. After much faffing i managed to get the moon on the screen in sharpcap but I found I could not focus using just the webcam direct into the focuser. When i popped in a barlow it worked fine (except for the thin wispy clouds that seemed to follow the moon all niight)

It was as if I couldnt focus in far enough.

I have seen things called focal reducers and was wondering if that is what I need???

Any words of wisdom would be greatly appreciated.

Chris

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It should focus ok without the barlow on the 130p. It is not easy at first as the focus point is different than when using an eyepiece. You will need to make tiny adjustments with the focusser but you should not need a focal reducer.

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Hi Chris, agree with the comments above, I used to have a 130p and had no problems using the webcam, you did well using a 2 x barlow as it reduces the field of view which would then be something like a 3 mm eyepiece

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thanks for the quick replies, i tried it 3 times, saw the image on the screen change colour so I know the moon was hitting the sensor but try as i might i could not get it in focus, when I was all the way in on the focuser it was almost there but i would need another quarter turn or so.

I agree that finding the sweet spot for focus is going to take rather a lot of practice together with an equal amount of not very polite words but it really was nowhere near.

Will try again tomorrow as long as i can see the moon i can play around.

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A focal reducer wouldn't help in this situation, it would just push the point of focus further inwards. Adding a barlow does the opposite and is the usual solution to get a DSLR to come into focus. A barlow would be a good idea anyway as this would give you a better imaging resolution.

Peter

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Same scope, same problem! However, I always use a Barlow now as I understand that that the recommended focal length for using the webcam is a minimum of 2000 - something to do with chip size and pixels I think. As the 130P is only f/l 650 this means a 4x is about right. I have had some success with Jupiter using a 2X and have just bought a 3X to try. However, it takes me so long to get Jupiter in the frame with the new one that I haven't had much luck yet - not sure I will ever try a 4X !

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Ah so that's what a focal reducer does. Sorta glad it's not just me.

A focal reducer does the opposite of a barlow lens and reduces the effective focal length of the telescope (reduces magnification). In doung so it also moves the point of focus inwards, a barlow lens will move the point of focus outwards.

Peter

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Very good.That has given me a bit more info on imaging.Iv got mono

modded Toocam & im looking for something a bit better in colour.

Steve.

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I've had loads of trouble with my Flextube 200p. The advice I found was to not extend it all the way, have ever so briefly tested that advice on mars and it seems to be good advice.

Sorry had in mind you had the flextube 130p, guessing not?

Edited by littlebeagle

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Hi again,

Having done a bunch of research I have found 2 possible solutions to the problem of not having enough inwards focus.

Both solutions were found on SGL !!

Solution 1

Move the primary mirror up the tube.

Solution 2

Shorten the focuser

Now I can't go fiddling with the primary on what is my wifes brand new telescope, so I am thinking of Solution 2 (aka plan :D

Found the info in a thread on here which links to a video on astronomyshed where he talks about the exact same problem and he suggests the following

Remove and replace the focus tube to eyepiece adapter threaded ring with a threaded m54 male to 2 inch barrel converter. this is going to save about 10mm

next is an antares 2 inch - 1.25 twist lock converter with the added bonus that if you unscrew the lock ring you find a t thread

So my question is this.....

Has anybody tried it on a 130p??

Cheers

C.

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I did not try to solve the problem when I realised that even if I could get it to focus directly the quality of the image would be poorer than if I used a Barlow as the focal length of the 130P is far to low for the size of chip in the webcam. I would use the Barlow even if I could get it to focus without as my only aim is to get the best possible image with the equipment I have. I can get it to focus using an extension tube (I unscrew the lens from the Barlow) but the end results are not so good so I don't bother.

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Have you checked the collimation of your scope? As said before, there is no problem getting an SPC900 focussing on a 130p. I have the images to prove it!

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I've got a 130 Astromaster and the focusing is fine on that with the SPC900.

It has the same f/l 650, I've used a barlow for Jupiter as well with no problem.

Here's my first pic of the moon from the other night.

Forgot to say that I use a DIY electric focuser that I've made from a R/C servo with a speed control for very fine adjustment,

it does make focusing so much easier.

post-29522-133877729021_thumb.png

Edited by cabby

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Please don't misunderstand me. I know it can be done, just not by me!

Just a thought though, I have seen 2 different focus mechs on the 130. One is mainly metal and the other is a moulded plastic type. The one I have is the moulded type. Could this be causing my problem? I can get focus (ish) with a Barlow.

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No. Mine was the moulded type and there was no problem. I know it is frustrating to be consantly told there is not a problem when clearly you are having difficulties. Are you able to focus accurately through the eyepiece? If that is ok then your collomation is probably OK. In that case it is probably either settings in the software or a lighter touch required. Sorry I can't be of more help but all I can suggest is that you find your nearest astro club and see if anyone can sort it for you.

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Okey dokey. I can get focus with 2 stacked 2x barlows and my 9 mm gso plossl. I can get focus with all the eyepieces with or without the Barlow. Telescope seems fine to me but what do I know :icon_salut:

Looks like it might be clear for a bit here in Rhyl so will go have another try.

Hope I crack this tonight.

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all righty then, i have been experimenting!!!

it turns out that if I remove the 1.25 inch collar (the bit with the 2 thumbscrews and hold the camera in the hole, i can get prime focus on the moon... yay.

I have moved the camera inwards by the height of the collar (less the threaded bit) and then holding the flange of the nosepiece tight to the end of the focuser I was able to get focus. I don't have a micrometer but i did a quick measure and the height of the collar is roughly the same as the distance of outward focus travel i needed which to my simple mind means that with the collar in place there was no way to achieve focus. I am so happy I have figured this out, now I need to find/make an adapter to fit where the collar screws in.

Happy Bunny.

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I could never get my SPC900 focussed in my 130P without a Barlow. :icon_salut:

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Tried your suggestion this morning and I was able to get focus on the moon with no problem. I used an old plastic Barlow with the lens removed (with the aid of a hacksaw) and wrapped some electrical tape around the barrel to make it a snug fit. I got the Barlow of AstroBoot a while ago to make a cheap extension tube. It looks like this one on ebay Seben Barlow Lens BA1 proven quality 31,7mm (1.25") | eBay and has a narrow band where the screw is located which my other Barlows don't have. Hope that helps.

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I have a friend who works at a photography shop that I am going to persuade to let me dig through all their old boxes of adapters to see if I can come up with something a bit more permanent but until then i am going to use the Force.

(Gaffa tape, it has a light side and a dark side and it holds the universe together)

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Hi,

Reckon I have sorted it now, one small hurdle to overcome but i'll have it finished real soon

We start with this

one.jpg

separate it and remove the thumbscrews

three.jpg

turn the bigger bit over

four.jpg

screw it back together

five.jpg

Now all i have to do is work on an elegant way to fix the camera in cos the thumbscrews are no good.

Can't believe it didn't occur to me sooner

Hopefully I can order another one of these adapters and leave it set up like this permanently

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