Query - $ for $ - what CCD / OTA would be best to capture planetary nebulae and why?

[g__day (Matthew)]

Simple question - but I expect it takes alot of know how to get the right answer for this. Put simply dollar for dollar - and ignoring considerable need for a capable mount and dark skies - what telescope design and CCD pairing would be best to capture planetary nebulae and why?

Lets say you a Paramount ME and you wanted to put a OTA and CCD on it to capture only planetary nebulae. What choices would you make if you had say 1) $5K to spend 2) $10K 3) $15K 4) over $20K.

I'm interested to know how experts would handle this task, what factors are of primary vs secondary importance and where the bulk of the spend goes at a price point - into the CCD or into the OTA.

Many thanks for your thoughts guys!

Matthew

[Peter Ward]

When you say planetary nebulae, does this mean you want high resolution, deep sky images of small angular size (6-60 arc sec) objects?

This imposes some considerable tracking/seeing constraints....mainly induced by the long (2500-3900mm) focal lengths you'll need to get some image scale.

Adaptive optics will help, but only if you can find a suitably bright guide-star for high frequency guiding.

You would not need CCD acreage, so a modest KAF402 or similar high QE chip would be fine. An SBIG ST7xme and AO8 would certainly fit the bill.

If you don't see any merit in AO, then any cooled (low noise) KAF402 system (Apogee, FLI etc. ) would do.

Hubble's WFPC2 comes to mind

[g__day (Matthew)]

Peter,

Thanks - I've enjoyed trying to capture the Triffid, Helix and Eagle in my second year of astrophotography. These targets are generally several arc minutes across. To go after really small targets I imagine alot of light grasp and precise tracking / guiding is needed. But say for faint targets in the 1 - 20 arc minutes field of view - if you already had a great mount - what would be your recommended OTA / CCD pairings at those price points please?

I doubt in the next 5 years my shots of the Lagoon will look like this - http://antwrp.gsfc.nasa.gov/apod/ima...rhaven_big.jpg (Fred, Martin and your shots alway amaze me!) but I'd love to know where to spend my $$$ if I get a windfall!

Matthew

[Peter Ward]

Matt,

OK...looks like you mean nebulae, rather than "planetary" nebulae. The latter apart from a couple of very large exceptions, tend to be well under an arc minute in size = really big scope to image well

My three rules of imaging gear would be "mounting, mounting, mounting"

If you can afford a high precision brand, eg Losmandy Bisque, Taka, AP. it is money well spent, as you'll be able to put any OTA you like on them later.

OTA's.....don't get hung up on aperture with CCD's. They are linear devices. All you need is more exposure time to get more signal.

There is at least one nutter out there who exposed NGC5128 for 19 hours

A high quality APO triplet in the 100 to 150mm range will do what you ask.

[g__day (Matthew)]

Echo that - so style of preferred OTA is a apo - not a SCT (because it gives you sharper images?), and CCD choice becomes less important once you enter a decent range?