Going to start imaging with C9.25. Guiding?

[kirkster501]

I really don't fancy OAG, it just scares me with all the faffing about with distances etc.

I am going to try using my CCDT67 telecompressor that will speed it up a bit (0.67) - anyone used this before on a SCT?  I think at F10 in the UK it's a none starter, images will just take too long for the skies we have available.

I reckon guiding with my Celestron 80mm guide scope should work OK - again, appreciate any thoughts?

I love the SCT for planetary and visual of GC, PN etc.  So it's worth investing in a Feathertouch microfocuser I think.

Appreciate your thoughts?

Steve

[PhotoGav]

Go for the OAG route. It really isn't tricky - the Celestron OAG is pretty simple to get working. It can be a tad fiddly to find a guide star, but that also depends on the guidecam sensitivity. At the 9.25's focal length OAG really is the only reliable option...

[swag72]

OAG isn't tricky - The first time I ever tried it was with the C9.25 and it was no where near as bad as I thought. I was expecting all sorts of issues and I was up and running for the evening!

The micro focuser was a good addition as well.

[Owmuchonomy]

Sound advice as above. Being a glutton for punishment I am however using my AA finder guider usually reserved for a much shorter FL frac on my 9.25 when the mood takes me....

M27 on my Flickr link was such an effort. Not really tried dimmer DSOs yet.

[Mav359]

My QHY5 9x50 finder guider on my 9.25 has never let me down, resonably cheap to assemble and use & works well with PHD even in my LP skies. I have found that balance is everything though and i get better results when doing a meridian flip by just re-calibrating rather flipping data.

I built a DIY motorised focuser for my 9.25 and it is the best thing i ever did.

[kirkster501]

With an OAG such as the Celestron one, is it possible to rotate the Prism/Guidecam assembly of the OAG whilst leaving the camera in the orientation it is currently in?  I envisage a situation where you frame the subject correctly with the imaging camera, only to have to start rotating things to find a guidestar and thus spoil the framing. Lets face it framing the subject can take a wee while, last thing we want to do is then disturb it...  This is what I meant in the OP when I mentioned a bit of a faff...

I would be interested in the workflow.

[PhotoGav]

Yes, you are absolutely right. Once you have the framing pretty much right, you then rotate the guidecam portion but not the camera portion, though you can't avoid a small amount of camera movement (or at least I couldnt!). A very sensitive guidecam will reduce the need to move it though as more often than not there will be a star suitable for guiding in view straight away.

This is the opportunity cost of reliable guiding I guess.

[kirkster501]

How would a QHY5 stack up to a Lodestar then Gav?  Could get pricey if i have to buy a Lodestar as well.

Anyone got a plan please of the totem pole of bits from the visual back of the SCT to the CCD sensor?  With and without reducer?

Steve

[PhotoGav]

I used a QHY5-II mono before the Lodestar and it works very well, but I am finding the Lodestar far more sensitive.

As for the exact imaging train - have a look at the manual which is in the 'support' section on the lower right side of this page: http://www.celestron.com/browse-shop/astronomy/astroimaging-accessories/guiders/off-axis-guider

[sloz1664]

Hi Steve,

I tried OAG with my old QHY5. Couldn't get focus and I felt the QHY5 wasn't sensitive enough. I now use a Lodestar/OAG to guide my TAL 200K  @ f5.2 (home made focal reducer).

I have guided the Tal with the QHY5L/9x50 finder guider without problems.

cheers

Steve

[kirkster501]

Thanks all for the replies - I might buy an OAG and see how I go before shelling out for a Lodestar.  The Celestron one looks good if somewhat expensive.  I approach the whole thing with considerable trepidation I must say....

Steve

[Guest]

My QHY5 9x50 finder guider on my 9.25 has never let me down, resonably cheap to assemble and use & works well with PHD even in my LP skies. I have found that balance is everything though and i get better results when doing a meridian flip by just re-calibrating rather flipping data.

I built a DIY motorised focuser for my 9.25 and it is the best thing i ever did.

Hi,

You say you guide you 9.25 with a 50mm finder, I have an 8" SCT @f6.3 about 1260mm focal length with the focal reducer, do you think I could use a finder guider for that, or is it too much focal length? Currently I use an ST80 guide scope, but it makes my set up very heavy, so,was looking for a lighter set up.

Interested to know you views on this, as I have asked the question on here, but never got many replys

Cheers

Olly

[glappkaeft]

I really don't fancy OAG, it just scares me with all the faffing about with distances etc.

 

I am going to try using my CCDT67 telecompressor that will speed it up a bit (0.67) - anyone used this before on a SCT?  I think at F10 in the UK it's a none starter, images will just take too long for the skies we have available.

The only distance you need to worry about with an OAG is that you can come close enough to focus. You can always move it further away if needed with extension tubes. In that sense it is even more forgiving than your reducer where it only works as advertised at 85 mm and you shouldn't go outside 70-90 mm.

[lensman57]

I really don't fancy OAG, it just scares me with all the faffing about with distances etc.

I am going to try using my CCDT67 telecompressor that will speed it up a bit (0.67) - anyone used this before on a SCT?  I think at F10 in the UK it's a none starter, images will just take too long for the skies we have available.

I reckon guiding with my Celestron 80mm guide scope should work OK - again, appreciate any thoughts?

I love the SCT for planetary and visual of GC, PN etc.  So it's worth investing in a Feathertouch microfocuser I think.

Appreciate your thoughts?

Steve

Hi Steve,

My concern is the use of CCD67 reducer on the SCT. The CCD 67 has the stated reduction factor for a fixed mirror system ( fixed FL ) such as an RC, an SCT has a variable FL due to the moving mirror. It does not flatten the field either so if you used a scope with a flat field it would stay flat and a curved field would stay curved. The 9.25 has a curved field so depending on the size of the sensor the effect could be quite pronounced. It would be interesting to see how you get it working.

A.G

[orion69]

Hi,

You say you guide you 9.25 with a 50mm finder, I have an 8" SCT @f6.3 about 1260mm focal length with the focal reducer, do you think I could use a finder guider for that, or is it too much focal length? Currently I use an ST80 guide scope, but it makes my set up very heavy, so,was looking for a lighter set up.

Interested to know you views on this, as I have asked the question on here, but never got many replys

Cheers

Olly

FL is not the problem, problem is usually flexure. Mirror systems are much more prone to flexure than refractors. Frankly I would never image without OAG on any system.

[Guest]

FL is not the problem, problem is usually flexure. Mirror systems are much more prone to flexure than refractors. Frankly I would never image without OAG on any system.

Yes I do agree totally with that, so flexure as side, do you think a 50mm finder guider with my system, with its long focal length.

And can I ask a favour, I see you are in Croatia, could you just visit my website here

http://www.ollyspages.co.uk

As I want to,check the visitor map on my site is working, from other countries aswell as UK, appreciate it.

Olly

[Mav359]

Hi,

You say you guide you 9.25 with a 50mm finder, I have an 8" SCT @f6.3 about 1260mm focal length with the focal reducer, do you think I could use a finder guider for that, or is it too much focal length? Currently I use an ST80 guide scope, but it makes my set up very heavy, so,was looking for a lighter set up.

Interested to know you views on this, as I have asked the question on here, but never got many replys

Cheers

Olly

Hey Olly

I never had an issue with it, as i said balance is everything for me. I use a hyperstar now & i have constructed a rather heavy dew shield to double as protection, add to that the DSLR on the OTA and mine is REALLY heavy, i had the balance spot on at 6PH and was guiding for 20mins

Balance, Rough polar align using the polar scope & then i use align master to get polar aligned i had no issues guiding beyond 10mins.

As Knez said FL isn't the issue, your either polar aligned or your not, the closer you are the less guiding has to do, then you can worry about flexure, collimation & focus etc

[orion69]

And can I ask a favour, I see you are in Croatia, could you just visit my website here

http://www.ollyspages.co.uk

As I want to,check the visitor map on my site is working, from other countries aswell as UK, appreciate it.

Olly

It's working...  

[Guest]

It's working...

Great thanks

Olly

[Christopher Davenport]

Hi,

You say you guide you 9.25 with a 50mm finder, I have an 8" SCT @f6.3 about 1260mm focal length with the focal reducer, do you think I could use a finder guider for that, or is it too much focal length? Currently I use an ST80 guide scope, but it makes my set up very heavy, so,was looking for a lighter set up.

Interested to know you views on this, as I have asked the question on here, but never got many replys

Cheers

Olly

I guide with a qh5ii on a finder guider, this allows me to guide up to 1250mm fl.

The thing is with centroid calculations the finder is not the limiting factor, but rather the mount. My mount is on its outer edge of stability at that FL.

I have reduced my MAK to 850fl with a 0.63 reducer and can get 500sec sub's, at which point again my mount starts to limits me.

[james_screech]

Go for an OAG it's simpler than some people think.

I've tried both a guide scope and OAG on my C8 and will never go back to the guide scope. Flex is a BIG problem with any guide scope setup. OAG distances can be worked out relatively simply before hand from the camera specs. Then in daylight focus on a distant object (I used a house about 40m away, so it doesn't need to be far)  refine the focus so that both cameras are in focus. Focus of the guide camera is not critical and can be slightly off.

With a guide scope I had tracking issues in 10-20% of my subs with 3 min exposures, with a OAG I can get less than 5%  in 5 min exposures and less than 10% in 10 min exposures.

James

[kirkster501]

OAG is something I am going to have to consider.  I have been less than impressed with the subs coming off my RC8 as well with a guide scope. 

[r3i]

OAG is something I am going to have to consider.  I have been less than impressed with the subs coming off my RC8 as well with a guide scope.

Hi Steve,

+1 for the OAG route. Yes there is a bit of faffing around at first to get the cameras parfocal but you can do most of it during the day by pointing at a distant target such as an electricity pylon. Once you've got it nailed you won't regret it.

I've been using a humble Meade DSI1 as my guide camera for a good while now and I've never failed to find a guide star though I've had to rotate the guide camera around a few times, particularly when imaging targets away from the galactic plain where there's less stars in the FOV.