What are my next steps? I can spend £125 every month.

[evilgeenius]

Hello All!

I recently bought my first ever telescope, a Celestron CPC 925. Since buying it i've taken a keen interest in astrophotography.

I want to buy some more kit to able me to take better photos. Based on me being able to spend £125 per month, what would be a good plan for the coming year (or two)? In terms of what equipment to buy and when. Obviously I can wait more than one month if required to save up some cash. Ideally I'd like specific advice such as what models of devices I should buy.

This is all my current equipment :

Celestron CPC 925 SCT

Celestron x0.6 Focal Reducer

Hyperion Mark III eyepiece - with T-adaptor

Celestron 40mm eyepiece

GH1 DSLR-like camera - with T-mount and T-ring for attaching to scope at Prime Focus

Bahtinov Focas Mask

Laptop

It would seem as though the first thing I should buy is a wedge. After that I'm not too sure. Though I think I need to be heading down some kind of autoguiding route.

Also I can't really wait years, ie you can't say "Wait 4 years til you've got enough cash, then buy XXX thousands of pounds of equipment".

Any advice at all is appreciated.

Cheers

Chris

[BlueAstra]

I started with a C8 sct. I first used an Orion OAG and Lodestar guidecam. you will also need a light pollution filter if near street lights. You may have a problem with rear space at high decs so a separate guide scope (st80?) may be better.

[ollypenrice]

For deep sky imaging you will need a wedge with your scope. You need to be at the equatorial angle to track, as I'm sure you know.

If you go down the road you are starting out on (trying to image through a fork SCT on a wedge) you should be aware that it is a road that does not end in success for all who try it. It didn't for me and I know a good few others who fell by the wayside. It is just hard to get them to track accurately enough but some do succeed. I know that is not what you wanted to hear so I'll move on to what you did ask to hear!

Wedge, as above. Expensive things so try for second hand.

O.63 focal reducer-flattener. Not much point in using DSLR type cameras at f10 and there is plenty of coma in unflattened SCTs on large chips. These, too, come up second hand. Don't look at the 3.3 reducer, they are for tiny chips.

Autoguider. An Off Axis Guider might be best at the long FL of an SCT but a guidescope would also work. The cheapest and best is the humble ST80 but here is an idea; learning imaging at long FL is difficult and getting good enough guiding is also difficult. If you went for a good cheap little apo guide scope you could reverse roles and image with the piggybacked apo while guiding with the SCT. The short FL will need far less accurate autoguiding than the long SCTFL. New guide cams are appearing all the time and getting cheaper.

Crayford focuser for the SCT in maging use.

Set of improvised weights to get the fork mount balanced.

Olly

http://ollypenrice.smugmug.com/

[evilgeenius]

Thanks for that Olly.

> It is just hard to get them to track accurately enough but some do succeed.

Why doesn't a guide scope or OAG with an autoguider camera solve the tracking issues? I thought that was their purpose?

Is there an issue with the actual mount + wedge and the tracking or is it just the long focal length of the scope?

> If you went for a good cheap little apo guide scope you could reverse roles and image with the piggybacked apo while guiding with the SCT.

What does 'apo' stand for? Can you recommend a good cheap one? Is the ST80 a apo scope? Is this the ST80 you meant : First Light Optics - Skywatcher Startravel 80 OTA ?

Cheers

Chris

[Essex Stargazer]

What does 'apo' stand for? Can you recommend a good cheap one? Is the ST80 a apo scope? Is this the ST80 you meant : First Light Optics - Skywatcher Startravel 80 OTA ?

Cheers

Chris

Chris

This may help re APO

Definition for apochromatic corrected lenses

[pete_l]

I want to buy some more kit to able me to take better photos.

Have you considered piggyback photography?

You can get an adapter (I think they cost less than £100) for your scope that will allow you to use your DSLR as a ..... camera!

Basically, what you do it fit the adapter to your 'scope and attach the camera as you do to a tripod. The camera then tracks the sky as the mount moves the telescope. With this arrangement you can take widefield views and depending on how much optical (not digital) zoom your camera has, you can get some quite nice shots of some DSOs.

Some advantages:

• Widefield views are less demanding of accurate polar alignment
  
• You get more stars in each photo
  
• You can practice image processing and get some nice, worthwhile results
  
• By taking lots of shorter shots and stacking them, you can start imaging before getting "wedged" - short exposures mean acceptable levels of image rotation
  
• You can still look through the eyepiece while imaging
  

Personally I quite like wide views of the sky. It gives me a sense of perspective and a lot of DSOs are surprisingly large - just faint. When I use my Nikon CP5000 point'n'shoot in this mode (it has a bulb setting for long exp) I've found that it's surprisingly sensitive. I have one image that I took in Tenerife that shows Neptune! It's only a dot, but hell, it's nearly Mag. 8 - I was impressed

Oh yes, you don't mention a webcam. You never know, you may be able to buy a piggyback adapter and a webcam in the same month. That's a sure way to guarantee an extended period of cloudy weather.

[ollypenrice]

Autoguiding is not always 'plug and play.' You are asking for an almost absurd degree of accuracy, maybe an error of around a tenth of a pixel on a typical ST80/guidecam setup. So many things conspire against you and the odds pile up the longer the focal length you are using.

There is an issue with the fork and wedge, yes. Wedges that I have tried to use have been hard to polar align because when you loosen the bolts to get them pointing in the right direction everything moves and when you tighten them everything moves again! It took me hours to get it right. Also the mechanical quality of commercial fork mounts is not that good. Lastly they are hard to get into dynamic balance so that the loading on RA remains constant in all positions of the mount. If you look at the imaging boards you will see hardly anyone using fork and wedge. The overwhelming majority are using German equatorials. But some do succeed, I readily concede.

A small apochromatic refractor might be the WIlliam Optics ZS72. I used to use a ZS66 (out of production) piggybacked on my SCT when I started. That worked out OK.

Never look at adverts or manufacturers' blurbs for advice. There everything works. Instead I'd advise a copy of Steve Richard's Making Every Photon Count.

Pete's piggybacked camera idea is a great one. I'll second it for sure.

Olly

[adamsp123]

RobH used to use a SCT and wedge but has changed to a GEM and refractor IIRC, maybe you could PM him and ask about the challenges regarding the type of setup you have.

Olly and others make many fine points including getting the book - Making every photon count.

To be brutally honest I think you may spend a lot of money on your present rig and get very very frustrated.

Auto guiding isn't "plug and play" more "plug and pray".

I have learnt the hard way and made many mistakes (I wish Steve's book had been out when I started), only now I seem to have got the bugs out my setup and waiting for clear skies to really have a bash....although the new Tesco store has scuppered my eastern horizon.

Good luck with your endeavours.

[antimorris]

As Olly said, not all get a fork-arm on a wedge to succeed, however I am one that has had success with it (I have a Celestron CPC800) ... it does take some patience and while you can practice and get started without a wedge (you will be limited to around 30sec subs) you really need to invest in a wedge (I also vote for getting one 2nd hand - I did and saved a bunch that way) and then be patient every night you set up on the wedge making sure you spend enough time to get a fine-tuned polar alignment if you want to succeed, especially at the FL the 925 has. Also - you will need a good weight set to get the dynamic balance fine-tuned. I do concede that I am one of the few that images without a GEM - but just wanted to let you know it is possible.

Also 2nd the .63 reducer - I have Celestron's and it works well for me.

While an auto guider is incredibly nice and saves a lot of headache once you work out the kinks, you CAN do long-exposure without it, even on the focal length the 925 (or in my case the 800) has. You just have to be incredibly **** about the polar alignment. Before I saved enough to get an auto guider I was able to get 8-10min subs if I really spent time on the polar alignment, though generally was able to get 5 min subs with consistency if I didn't want to spend a long time on the alignment. So it CAN be done - you just have to work at it and be patient and be willing to put up with a good bit of frustration and keep chugging away. I wasn't able to spend more right away (similar to the initial budget you state) so I was bound and determined to do it with what I had. Granted I find it MUCH easier now that I have the additional gear (OAG, auto guiding camera, guide scope depending on my setup, CCD, etc) but got decent results before I had all that.

I don't have a crayford on my SCT but I do have a Feathertouch micro-focuser - I would suggest one or the other for sure. You need to be able to fine-tune the focus.

You should be able to find an astronomy club or at least some like-minded folks near you to help you out if you have problems - I have found people in this hobby generally (I have found some very rude exceptions) are happy to help out others so don't hesitate to ask for help if you need it or want a second pair of eyes.

Since I do image with the CPC I am happy to field any questions you come up with - just shoot me a PM.

[ollypenrice]

Anna, I'm astonished and impressed that you could get those unguided times at SCT focal length. It's pretty much unheard of, I think, but hats off, nice one! Maybe they have improved since my attempts, which were with Meade rather than Celestron.

Olly

[antimorris]

Olly -

It is pretty unheard of, from what I hear, but I was adamant as I didn't (and don't) have the money to get at GEM and it took me a while to save the money with a move and a baby to get an auto guider. I just wanted to make sure that others know it IS possible, just takes a bit more work.