Is it me or is the moon out of focus ?

[slim mole]

After my first attempt at AP (iPhone to the eye piece) I decided to invest in an adapter and T ring for one of my Canon EOS DSLR's.

Tonight was the first night where I had a chance to have a play, and I think I'm missing something. Set up the telescope as usual, located the moon (not too difficult). Removed the eyepiece and popped in the camera into the resulting hole. 

But nothing I did seemed to enable me to get the moon in focus, all I could get was a grey blob where the moon should have been. Eyepiece back in and there it is, craters, cream cheese and all. A bit more playing and with my Barlow in the tool chain I could get it in focus, but obviously now only seeing a smaller portion of it.

From my experimentation it would seem that to obtain focus I would have needed to get the camera closer to the secondary mirror than the focus mechanism on my Skywatcher 130p would let me go.

Am I missing something ? Any insights appreciated

Moley

[Scooot]

Have you a spacer in your draw tube that you can remove. That's what I had to do in my very limited experimentation in A photography?

[stelios_t]

Rather strange, as I find I need more out-travel for my focuser when using the camera as opposed to diagonal + EP. 

Are you using a T-ring and prime-focus adapter to attach the camera? I hope you're not putting the camera where the eyepiece goes in the diagonal. 

[Avocette]

Hi. I believe it is not possible to get your DSLR sensor to the prime focus of a 'standard' SW 130p. That's why SW sell the 130PDS with a slightly shorter tube and a larger secondary mirror (plus a Dual Speed focuser). One option would be to move the primary mirror up the tube, but you may feel this is quite a significant modification and then the secondary mirror will not 'see' all the light from the primary.

[Cornelius Varley]

It's definitely you. The 130P, as do many other reflectors, cannot reach focus with a DSLR. The two solutions are either, use a barlow to move the point of focus farther out (this you have already found out) or, move the primary mirror up the tube (only recommended if you know what you are doing). You might also try unscrewing the barlow lens from its barrel and screwing it into the camera nose adaptor. This will give you a smaller increase in magnification and move the point of focus outwards.

[slim mole]

Thanks for the information, looks like for the short term I will be using the Barlow. I hope this will let me get up to speed with AP.  

Any suggestions of deep space objects that I can use as training tools to get the feel for the combination of telescope (SW130p ... With barlow !), Camera (Canon EOS 400D) and software (Nebulocity)

In the long term I do have a vague plan to upgrade to something like a 200PDS, I am assuming that this would provide the 'plug and play' capability I thought I could get with the T-Ring and my DSLR ?

.

.

I don't think I have a spacer in my draw tube to remove (but to be honest I have no idea what one looks like, but there is precious little in the focusing assembly to remove)

[Herbig]

M42 is usually the next target after the moon!

[Avocette]

Ironically you don't actually need the PDS version of the SW Newtonians that are a bit bigger than yours to reach focus. I have no problems focusing my (standard) 150p and I'm pretty sure this applies to the 200p as well. But there may be other disadvantages such as (I'm guessing) the risk that the focuser tube protrudes into the path of the light to the primary mirror on the standard versions when you succeed in focussing the DSLR. And of course the PDS models offer more precision with their Dual Speed focusers (although you can always upgrade a single speed focuser at a cost).

[slim mole]

I had another stab this evening before the moon came up. Could get M31 in my 25mm eyepiece, but when I swapped for the DSLR & Barlow combo I had nothing to focus on.

Took a few shots @ 30 & 60 second, but just got a vague suggestion of something very out of focus.  More success with Vega and Altair, I could see them in the cameras viewfinder, so was able to focus (sort of). Will have another look at the images in the cold light of day. Starting to realise there is more to AP than just bunging a camera on the pointy end of my telescope. Still I think I am learning . . . . . others may beg to differ !

Turned my attention to getting to grips with the sky in general, and managed to find M2 pretty easilly, then got my 11 year old assistant and sometimes PIA to point my scope else where, then see how long it took me to get back to M2. She gave up waiting for me to find it again, but I did.... eventually . . .  honest. Its amazing how much the moon spoils what can be seen.

I think AP will be shelved until I make my mind, upgrade the OTA or go for a GOTO on the mount. . . . .  . decisions decisions !

M42, sounds like a target for tomorrow night, weather permitting

Moley

[ronin]

I think Skywatcher have a habit of saying you can attach a DSLR, what they don't say is that you may not be able to focus an image on to the DSLR.

[Avocette]

I had another stab this evening before the moon came up. Could get M31 in my 25mm eyepiece, but when I swapped for the DSLR & Barlow combo I had nothing to focus on.

Took a few shots @ 30 & 60 second, but just got a vague suggestion of something very out of focus.  

Hi Moley. You haven't mentioned which mount you are using - presumably it's motorised/tracking if you're attempting long exposures at such magnification?

[Cornelius Varley]

I think Skywatcher have a habit of saying you can attach a DSLR, what they don't say is that you may not be able to focus an image on to the DSLR.

The 2" focusers have a direct attachment which does work. It is the smaller reflectors with the 1.25" focuser (130P/130/114) that have the problem.

[slim mole]

Hi Moley. You haven't mentioned which mount you are using - presumably it's motorised/tracking if you're attempting long exposures at such magnification?

HI Avocette,

Its an EQ-5 with a single RA motor. It seems to track pretty well, even with a cursory nod in the direction of polar alignment.

Main issue I have detected from last night seems to be 'mirror slap'.  So looking into the settings of my camera to lock the mirror up.

If the weather is good tonight I think I will hook up to an old laptop which I am installing Nebulocity on, then see if I can get multiple images of M45 to play around with.

Moley