1st attempt at DSLR at prime focus...but live view blank?

[Notty]

First time attaching my EOS1100D to my SWED80-DS, bahtinov mask at the ready and a lovely clear evening and I'm full of excitement at my first attempt at a DSO, however when I attach the DSLR to the scope and switch on live view (centred on vega in the eyepeice beforehand) there's nothing but a black screen with a small white outline rectangle in it. I can't get any indications of the star whatsoever. Anyone know what I'm doing wrong? exposure set to bulb, ISO1600 and screen brightness set to max and min but no avail. Tied slewing around to see if it wasn't quite centred but no avail.

Obvious howler check, I'm straight into the focusser tube (not using the diagonal, though I tried with it as well) and I've tried focusser travel all the way forward and all the way back. I'm guessing the correct position would be pretty much fully in.

Anyone know what I'm doing wrong? Any advice appreciated.

[Tinker1947]

Did you check through the 1100D view finder that Vega was still in view, its bright enough that you should be able to focus without using Live View......

[Thalestris24]

Hi

I don't have an ED80 but it sounds like a focus issue. I suspect that if it's normally used with a diagonal that you need to make up for the missing distance with an adapter/extension tube. I'm sure an  ED80 owner here can confirm.

Cheers

Louise

[Leveye]

You might have to try on a night with the bright moon out and while holding the camera up to the focus tube move it in and out to see where it's focus point is. As said before you might need an extension tube to reach focus.

[Thalestris24]

...Or you can experiment with it during the day if you can sight a distant object

[D4N]

Yeh I always test out new set ups in the day to make sure it actually works

Just remember the focuser needs to travel in a little bit from far focus to reach infinite focus.

[PeterCPC]

I think that you would find it easier to use the camera through a laptop using Backyard EOS or APT. Your screen will be bigger and you can control it without touching the camera which must be set to Manual.

Peter

[Notty]

Hey thanks for all the replies everyone. I'll have to check but I think the OTA bits and pieces/guidescope dovetail etc obscure the viewfinder when it's attached. I might just have to try APT or the other one. I always assumed I just plug the camera straight into the focusser tube but as Louise said, taking out the diagonal is suddenly losing loads of distance. I'm sure all the pics I've seen of this setup have it connected straight to the focusser tube though! If anyone's got the same setup I'd love to hear how it's all supposed to fit!

[Tinker1947]

This is a ST-80 with a CCD plugged in the end, it has 2 extension tubes plus a 1.25" connector, then add the extra space a DSLR needs over a CCD to get the sensor in the right position you could be looking at 4" or more from the focus end of the tube to the sensor.....

[Notty]

Gulp. But I thought the SW ED80 DS was designed specifically for AP? And yet it still needs this Heath Robinson stuff to achieve focus? Calling any ED80 DS + EOS owners!

[Hitesh]

I've got an ed80 and don't have that problem. If you are going to do imaging you really do need a focal reducer, if you want to keep the native focal length then you need a 2" extension tube and you should

be fine. I use the Williams optics 2" extender but there are loads about

[Thalestris24]

This is a ST-80 with a CCD plugged in the end, it has 2 extension tubes plus a 1.25" connector, then add the extra space a DSLR needs over a CCD to get the sensor in the right position you could be looking at 4" or more from the focus end of the tube to the sensor.....

Hi Tinker

I've previously used my ST80 with an 1100d but it only needed a single 40mm extension tube - remember the extra dslr sensor distance will reduce the need for additional added spacing plus there's a fair amount of focusser travel available  Mind you, I can't really comment on the ED80 - I must get one of those one day!

Louise

Edit: having done a little research it looks like you don't need an extension tube on the ED80 if you have the focal reducer fitted

[Notty]

Ok thanks all. So I either need an extension tube or a focal reducer, and apparently this is to be expected. I have a coma corrector for my 200pds and this is apparently a focal reducer also. Does anyone know what unpleasant side effects if any of using it on a refractor which doesn't need it would be? Or do I need the dedicated focal reducer?

Thanks again for the input everyone.

[Thalestris24]

Ok thanks all. So I either need an extension tube or a focal reducer, and apparently this is to be expected. I have a coma corrector for my 200pds and this is apparently a focal reducer also. Does anyone know what unpleasant side effects if any of using it on a refractor which doesn't need it would be? Or do I need the dedicated focal reducer?

Thanks again for the input everyone.

Hi

You can't use a coma corrector in place of a reducer/flattener! The former is for reflectors, the latter for fracs.

Louise

[Notty]

Thanks Louise.  Oh well it's been a few days since I last gave FLO some money 

[Notty]

Thanks Louise.  Oh well it's been a few days since I last gave FLO some money 

...that is, if I really need one yet?  I've found a 2" extender, assuming I can get focus now, am I right these field flatteners just basically tidy up the stars on the corners?  Also what's the advantage of capturing at F6.37 down from 7.5 with the reducer?

[Tinker1947]

Shorter sub times, if you want to go lower get a 8" Newt...

[Notty]

That's interesting, I've got an 8" newt ie a 200PDS which I use for visual, mainly looking at the planets!  I thought the ED80 was the bees knees thought when it came to deep sky targets, which is why I got one.

I am sure I should know this then, but what are the relative merits of the two scopes (ED80 vs 200 PDS) for deep sky AP? I know the collimation needs to be bang on but I'm not afraid of that.  I always assume the ED80 had a wider FOV for the larger targets like big emission nebulae etc is this correct?

For a target like Andromeda then, which would give a better result do you think?  Sorry for drifting my own thread!

[Tinker1947]

You can set-up Stellarium with both scopes ED80/200PDS, and it will display the FOV through each or use the FLO Field of view calculator .....

http://astronomy.tools/calculators/field_of_view/

[Thalestris24]

That's interesting, I've got an 8" newt ie a 200PDS which I use for visual, mainly looking at the planets!  I thought the ED80 was the bees knees thought when it came to deep sky targets, which is why I got one.

I am sure I should know this then, but what are the relative merits of the two scopes (ED80 vs 200 PDS) for deep sky AP? I know the collimation needs to be bang on but I'm not afraid of that.  I always assume the ED80 had a wider FOV for the larger targets like big emission nebulae etc is this correct?

For a target like Andromeda then, which would give a better result do you think?  Sorry for drifting my own thread!

Hi

Probably the ED80 would give a better result for M31 as it's a big galaxy - much bigger than a full moon! However, the dust lanes are faint and need long exposures... The f7.5 ED80 has a fl of 600mm compared to 1000mm on your pds so a wider field of view with the ed80. Even wider and faster with the 0.85 reducer!

Louise

You don't have to get the flattener/reducer straight away but I think it will need exposures 2.25 longer than your F5 200pds would.

[Skipper Billy]

I have the 200PDS, the ED80 and a Canon 1100D - the attached (hopefully!) photos show the framing you can expect of M31 with an ED80 with and without a FF/FR and with a 200PDS - its easy to frame with the FF/FR, a bit too tight without it and not possible with the 200 PDS.  The ED80 is a cracking wee scope for imaging, the 200PDS is just too big and acts like a sail in any breeze at all. I have never tried to use the camera straight to the scope - I always use the FF/FR and no extra spacers are required. I can post photos if it helps.

[Notty]

Thanks for the tips all, I have learned lots from all your input.

[Notty]

and Billy, if I could take you up on your kind offer of pics of your setup that would be awesome!  That Stellarium tool is brilliant I must learn these packages in greater depth... along with APT, CDC, SharpCap, EzPlanetary, PHD2, Deepskystacker, EQMOD and all the other millions of packages that one seems to need to know!

[Skipper Billy]

Here you go - excuse the poor quality phone pics but my real camera is in the photos !!!!

[CosmicOrangutan]

Hi Notty, 

I had the same issues getting live view on my Canon to show any stars to focus on. I found that setting the ISO higher to say 6400 and setting a longer exposure time began to show stars that you can use to focus on. Then when you are aligned and ready to image just change your settings back down to 1600/800 ISO and away you go.

note: even with the higher ISO live view will detect only the brightest stars.