M13

[shaula]

Hi,

We had a lovely clear night on Sunday so we stayed up & trawled the skies.

We found the M13 which looked clear and well detailed but small through the 70%FOV 38 superwide angle lens so, thinking we'd be able to see it close-up, swapped the lens for the 9mm Plossl & 2xbarlow but couldn't see anything!

Can someone tell me how we can get a better look at it next time please?

cheers

Claire

[Psychobilly]

Probably made to big a jump im magnification so lost M13.... work your way up in stages...

Peter...

[drummerp]

Probably made to big a jump im magnification so lost M13.... work your way up in stages...

Peter...

Hi Peter,

Actually, we did go down through the eyepieces, 20, 15, 9 and tried them with and without the 2x barlow, the image did become much larger but it stayed fairly blurred, any suggestions why this was ?

Cheers

Neil

[Psychobilly]

Please excuse a silly obvious comment... you did refocus between EP's?

M13 is such a mass of stars I suppose they blend together... I'm trying to remeber what it looked like through Rob H's 14" with Lulu's Ethos at SGL4...

Whats the collimation like?

[drummerp]

Yes we did re-focus between EP's.

I was thinking that, could it be the quality of the eyepieces ?

Or could it be the fact that there was a lot of light pollution arround ?

I also remember how it looked so clear at SGL4 with Alex's 12" dob and Johns 100% FOV eyepiece.

Cheers

Neil

[Doc]

I would imagine it just drifted out of your FOV and you lost it.

The fov of a 9mm would be very narrow and M13 wouldn't last long in it.

[drummerp]

I would imagine it just drifted out of your FOV and you lost it.

The fov of a 9mm would be very narrow and M13 wouldn't last long in it.

We could still see the M13 even with the smaller mm eyepiece but it was just blurred and we were unable to focus, even on the stars nr by and arround it ???

Cheers

Neil

[kniclander]

maybe your scope is out of collimation? It wouldn't really show at low power but would make stars smeary at higher powers. Try focussing on a bright star at high power 150+ (Polaris is a good one cos it doesnt move...) and focus in and out and you should see concentric light and dark rings - if the rings are not round then you should check collimation.

ps don't worry if the image "boils" - that is just atmospheric turbulence

pps I suspect that at high powers globs will always look a little "smeary" as the stars are so close together.

[Jarndyce]

I suspect that a 9mm EP with a 2x barlow is probably pushing the maximum magnification you can achieve with your scope, and won't really give the best result with M13. You probably noticed that the image also gets progressively dimmer as you increase the mag. This is where those with dobs will all chant that "aperture is king!".

Well they are correct.

Go with all the suggestions above, check collimation and focus and then try again.

My SCT (1500mm focal length) works best with either 70 degree 24mm or 16mm on M13.

With these, you can clearly see the "granularity", individual stars and wisps in the cluster.

I would recommend you don't use a barlow and see how you get on.

[drummerp]

Funny you guys should mention collimation.

As you know we have a campervan and we went away in it the weekend gone with the scope's in the back. When we arrived all 3 large collimation screws had come undone and fallen onto the floor of the van.

I screwed them all back in. Now I dont have a collimation eyepiece so I just looked through the focusser during the day and tried to make sure the small circal was centralised and then I make sure the screws were tight.

This therefore may be the problem. I might need to collimate the scope properly.

Would this do the job ?

Collimation - Celestron ColliCap

or should I purchase something a bit less cheap ?

Cheers

Neil

[Psychobilly]

This therefore may be the problem. I might need to collimate the scope properly.

Neil

I would say definitely based on the fact the screws had come out and you just screwed them back in....

[drummerp]

We i didn't just screw them back in, I did try and collimate it as such, I think I must have failed.

Cheers

Neil

[proflight2000]

It would not hurt for a quick fix to use an old cap from a 35mm film cannister, put a small hole in the center of it and take a look through. I have found with M13 that a 25mm eyepiece is ample, it gives you the wider view. The game is to basically just keep staring into it. Dont focus your eye on anything in particular, just allow your eye to suck in the whole area. You then will actually see more.

[drummerp]

This evening we collimated the 12" scope as best we could, this time we aimed for the M5 Globular Cluster as it's only MAG 5.80 I could find it quite easy but the image still appeared blured/fuzzy. We were unable to make out that it was a Globular cluster just a big fuzz ball and this was the same with all our eyepieces.

To me, it looks like we cant focus into the image properly.

Does anyone have any further suggestion or are we just expecting too much ?????

Below is an image I took of Google images of the M5 but I have made it look similar to what we can see through the lens so people my understand a bit more although, to be honest thats actually better then we can see.

Cheers

Neil

[John]

I've been looking at M13 with my 12" Lightbridge dobsonian this evening. It appeared like a photograph with hundreds of stars resolved. This was using the 13mm Ethos and a 9mm Nagler which seem to provide optimum magnification for globular clusters.

If your 12" scope does not show something similar, even with regular plossl eyepieces then I reckon it needs to have it's collimation adjusted.

Your 130mm scope should show some stars resolved at the edges of the brighter globular clusters as well so maybe collimation is also an issue there as well.

John

[drummerp]

I think we are gonna have to go to Ace Cameras in bristol this weekend and purchase a good quality collimation eyepiece to sort out the scope.

Cheers

Neil

[John]

I think we are gonna have to go to Ace Cameras in bristol this weekend and purchase a good quality collimation eyepiece to sort out the scope.

Cheers

Neil

I've sent you a PM Neil.

John

[drummerp]

I went for the more expensive option, The Baader Lazer collimation eyepiece, This hobby is costing me a small fortune lately.

I've spent the last hour reading the manual and collimating the scope, not an easy task for the first time during day light. It was way off so hopefully that was why we were seing blured images. I will let ppl know after tonights viewing session.

Cheers

neil