DSLR prime focus

[neilm]

Okay, got myself a DSLR and in anticipation of my T mount and T ring arriving I removed the lens from the camera, removed the EP from the scope but left in the dialectic diagonal, held the camera to the diagonal took a snap. All very nice, good image size, good quality, happy!

T ring and mount arrive, stick them on the camera, whip out the eye piece from the diagonal pop in the T mount, and yes you've guessed it, can't get focused.....too long I guess.

Take out the diagonal, yes fine, can focus, must get my eyes tested though!

I guess I have a couple of options.

1. A very very short T mount that I can use through the dialectic.

2. Don't use the dialectic, it's doing nothing for you, why leave it in!

Assuming 2 is the answer, Id like to increase the image size...so...

1. Standard 2 or 3 x barlow

2. I've seen a T mount with a built in barlow, that sounds quite good.

I decided to get a 2" T mount on the basis that gives more than a 1.25", but 2" barlows seem far and few between and I've yet to see a 2" barlow T mount with a built in barlow. So, swallow my pride and drop to 1.25" for a built in one or hunt down a good 2". Or just get a 1.25" T mount as I've already got a 1.25" barlow.

And finally, yes, I have just order every photon counts!

Cheers

Neil

[chiltonstar]

To increase image size, you can use a 2x teleconverter for the DSLR (if you've got one) between the camera and telescope. The quality of these can be very good, certainly better than some Barlows..

Chris

[brantuk]

The Antares 1.6x 2" Barlow is very good but I didn't try it at prime focus yet. I put it in front of the diagonal and a T-ring to 2" adaptor does the job with the Meg 72. Without the diagonal and at prime focus I use a WO 2" 55mm long Extender - hope that helps

[jgs001]

Remove the diagonal, I've played with using the diagonal and an SLR and it's always seemed rather precarious, not sure why, given my ep's are Hyperions... A 2x barlow will actually give you a bit more than 2x, given the distance between sensor and barlow lens element, that can be ok though. As has been said a 2x teleconverter will give you 2x, and there is another benefit. It's parfocal with the SLR, meaning you can use with or without the TC and if you're careful you won't have to refocus.

[neilm]

Thanks folks, plenty to think about, basically you need to spend more money! That's okay I was expecting that, I guess when you start out on something new it does always take time to accumulate the basic bits and pieces you need.....one day it'll all be there, maybe....

Cheers

Neil

[jgs001]

The 1.25" barlow may work nicely, it depends on your target... If it's the moon at night or dusk, the vignetting won't be noticeable, you're exposure it way to short to pull in the sky colour. You will get vignetting for a blue sky moon though. It's worth keeping a look out on ebay for a TC in something like an m42, pentax K or Oly OM mount, I think you'll be looking at about £30 for the TC and probably £5 for the mount converter.

[neilm]

Sounds good to me, plan of action is get a 1.25" T mount as I've already got the barlow so can give that a go and at the same time keep and eye out on ebay for a TC.

Cheers

Neil

[jgs001]

Even better if you can find a TC for your camera mount at that price, but if you do you will need to put insulation tape on the contacts of the TC or the camera does weird things as it can't find a lens...

[neilm]

"the camera does weird things as it can't find a lens..." I think I came across that tonight! Thanks for the tip.

Cheers

Neil

[ollypenrice]

What are all these Barlows doing on the scene?? Get 'em outta here! If you are imaging deep sky you will be killing your f ratio and that's what gives you your light.

What your Megrez 72 wants for deep sky is an anti-Barlow, namely a flattener reducer.

If you are not imaging deep sky then ignore me!

Olly

[neilm]

Thanks Olly, don't worry I'm am going to get the barlow out of here! I'm trying a few bits and pieces, as you do with a new camera, so I tried a bit of lunar first which is kinda why I'd like to get the image larger and not have to worry about light loss, hence the Barlow.

I've yet to have my first go at DSO, I spent my lunch break today looking through the imaging DSO forum trying to work out a likely first target, any suggestions gratefully accepted.....no barlow or TC!

Cheers

Neil

[ollypenrice]

Thanks Olly, don't worry I'm am going to get the barlow out of here! I'm trying a few bits and pieces, as you do with a new camera, so I tried a bit of lunar first which is kinda why I'd like to get the image larger and not have to worry about light loss, hence the Barlow.

I've yet to have my first go at DSO, I spent my lunch break today looking through the imaging DSO forum trying to work out a likely first target, any suggestions gratefully accepted.....no barlow or TC!

Cheers

Neil

Phew, Barlows are fine on that horrible big bright thing!

Big DSLR target for a Megrez 72? Seven Sisters? Double Cluster?

Sword of Orion?

Olly

Nice widefield target

[neilm]

Thanks Olly, suggestions taken on board. I'm might even post the results, well one day...when I've got the hang of it!

Cheers

Neil