That inward travel thang.....

[Digz]

Well, I had my scope out the other night and thought I would play about with my DSLR and T adapters etc.

Everything connected easily however I found there was not enough inward travel on the focus knob to get Saturn in focus. The way around this was using the Barlow however this was at the cost of having greater magnification making Saturn harder to locate for a newb like me, lol.

My question is whether this is suitable, (I imagine I will want the increased magnification at some point) or whether people have better methods of achieving enough inward travel?

For reference my scope is the Skywatcher 250P DS.

TIA.

[Peter Drew]

The Barlow solution is certainly the easiest, raising the primary mirror to bring the focus further out is the next in order of difficulty and another option is to replace the current focuser with a low profile unit but this can be expensive. In any event, the image of Saturn will be very small using a DSLR so you will need all the Barlow power you can muster.

[Shibby]

My solution to imaging is the same - a 2x barlow. One thing I can recommend if you wish to keep the magnification as low as possible, get that barlow lens as close as possible to the sensor - I managed to increase my FOV a little by doing this. Note the ends of barlows can usually be unscrewed. I was able to then screw it directly onto my T adapter. I don't know if there are negative side effects to doing this, but it seems to work ok for me.

[Digz]

Hey Peter / Shibby, thanks for the responses.

I must admit with the barlow Saturn certainly was small on the sensor!

Ive never thought about moving the mirror, however given my two left feet and hands I would avoid this as knowing me Id find a way to muck it up, lol. As for a low profile focusser this is something to note, however the missus will kill me if I spend any more money at the moment.

Again thanks for the input guys, much appreciated.

[adamh]

I thought the whole point of the DS range of scopes was that they had "better" focusing for imaging?

I'm a bit worried now, as I've been looking at a 200P DS to use for imaging (and visual) with a DSLR. How will I know if it can focus?

Adam

[themos]

What's the farthest object that you CAN focus?

[Digz]

I thought the same too Adam.

Im hoping to get the scope out again tonight and maybe try imaging the moon so Ill see if it can focus on that without the Barlow. I might also try adding a TC to be camera body to see what that does.

[adamh]

Hi Digz,

Did you ever get the weather and time to test this? I'm itching to buy a 200P DS and would hate to not be able to focus my DSLR!

How are you attaching the camera to the focusser?

Adam

[superjody]

i had the same problem with my skywatcher 250....then i realised that i could unscrew the 1.25" adaptor to reveal a t thread...problem solved it goes straight on and gets perfect focus, found this out after buying an adaptor i thought would work but didnt....[removed word] ha ha

give it a go and see if it works, might depend on your focuser though

Jody

[Digz]

Hi Adam - Ive still been using the barlow to achieve prime focus (I needed this for my moon mosaic as well.) given the moon is gonna be the closest object Ill be focusing on.

Jody - appreciate the response, I was unaware of this. When you say unscrew the 1.25" adapter is this the one supplied with the scope? Are you able to post a pic? Ill have a look at my scope tonight when I get home.

[sgazer]

if it helps, my 150p-ds focuses with a 1000d no problem and I think the ds range have been made specifically to allow DSLRs to focus (QUOTE: shorter tube length with the secondary mirror positioned closer to the primary mirror for more convenient prime-focus photography. ). I have about 10mm of travel left. Might be best if you can post a photo of your setup. The best option is to get a 2"-SLR adapter such as this;

Adaptors - Max DSLR Camera Adaptor

remove everything from the focuser draw tube apart from the silver draw tube itself and the black ring with the 2 thumbs screw in it and insert your 2" adapter (camera connected) into here. The then gives you the flexibility of using 2" or EOS clip filters.

However, if you get serious about imaging, you'll probably want a comma corrector, which are typically 2" with a T-thread to the camera (eg Baader mpcc), hence you'll only need one of these

Adaptors - T Rings

which the comma corrector screws into and then inserts directly into the draw tube and still allows the use of 2" or EOS clip filters.

[superjody]

Jody - appreciate the response, I was unaware of this. When you say unscrew the 1.25" adapter is this the one supplied with the scope? Are you able to post a pic? Ill have a look at my scope tonight when I get home.

as far as im aware its the one supplied with the scope, i bought mine secondhand.

i wont be able to post a pic yet but i think you would have tried it yourself by the time i do

[Digz]

Hi sgazer, thanks for the response. I already have an MPCC and still could not achieve prime focus (although I admit I was fumbling about in the dark screwing bits and pieces together to get prime focus)

Thanks for the reply Jody, Ill have a look now Im back at home

[Digz]

Well the 1.25" adapter does indeed have a piece that unscrews to allow me to attache my T-Adapter onto it. Now all I need to do is wait for some clear skies to try it out!!!

In the mean time am I right in thinking because I have unscrewed this section and brought the cameras focal plane closer to the mirror I will not need so much inward travel to achieve focus? Thus, hopefully, resolving the issue?

[superjody]

i havent tried it on deep sky objects yet but i got perfect focus on the moon

[Digz]

i havent tried it on deep sky objects yet but i got perfect focus on the moon

Sweet, roll on the clear skies!!!!