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telescope for photometry (PMTs)

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telescope for photometry (PMTs)


We are planning to set up a ready to go kit, including telescope + photometer + courses & practicals guidelines.

This will be aimed at emergent countries universities who have a physics/maths department and would like to develop astronomy but don't have access to any facilities and have limited budget.

The practicals will be on differential photometry and variable stars.

We will be using SSP photometer from Optec.

If you have any adviice from your experience about what telescope will give the best setup (Reflector/Refractor, cassegrain/newton focus...) ?

We would like to have an optimal setup option as well as a budget one (still allowing valuable scientific observations).

Thanks a lot for any input you can provide me with.



rth's picture
Photometry and Optec


I have some experience doing PEP using the Optec SSP-4-- I can give my two cents worth of advice.


WGEinWVA's picture
photometer setup

I have an SSP and have used it on a Vixen VMC260L quite a bit.  No doubt, a short tube SCT or cassegrain has some advantages as far as keeping everything balanced.  However, I have used the SSP on a 102mm Skywatcher ED refractor with good results, though of course it was quite limited in terms of the brightness of stars I could shoot with it.

I never used the SSP on my reflector as most amateur reflectors are going to tend to be pretty unbalanced with something of that size and weight sticking off the side.  But, you could use the SSP on most any scope if you really wanted to.

The scope in this is just a photon collector.  You will find that effective photometry will be more influenced by the mount.  You don't need the drive accuracy that you need for CCD imaging, but still, electric slow motions are a very great help in centering the star in the reticle.  I would not want to do it without them.  I was only using a cheap Chinese mount, with a fair drive and good electric slow motions, and it worked fine despite being overloaded with Vixen and photometer. 

You also have to consider the height the eyepiece on the SSP will be at and make sure it will make for comfortable work.  PEP can be fun but you have to get a good setup.  It will be very tedious and no one will want to do it if the setup is not comfortable. 

You will need the right charts for your targets. You also need a good finder to use to put the stars into the field of the SSP - this is an absolute must.  An 80mm is a good idea.  The correct image right-angle finders they sell these days which are not mirror reversed are great.


Recommended configs

I'm a new member interested in both visual and variable star astronomy.  

Investigating choices before purchasing.  Portability is a major factor for me.

Wondering what telescopes and SSP configurations have been tried, ruled-out, and which would be recommended.  Results?


KTC's picture
Are you considering CCD (or DSLR) photometry also?

Are you considering CCD (or DSLR) photometry also?

SSP photometers are not can be difficult to monitor telescope pointing unless you add some sort of imager...and if that's the case, consider using the imager as the photometer...unless you have a scope that points so well that you know your targets land within the SSP's sky aperture all the time.  (And that is more challenging with a portable rig.)

If you take care in testing, evaluating, and tweaking...just about any optical tube can be used for photometry.  Baffling and stray light control are important, no matter what detector you use.

Do you have a fixed budget?  Do you already have a scope/mount?  Do you have size/weight constraints? 

Portable rigs for 'machine-based' photometry can be problematic...alignment, etc. each night you set up at a new place, then take flats for calibration, and a bunch of other stuff.  A permanent rig makes life much easier.  I would not want to run a portable photometry rig unless I was chasing minor planet occultations that force you to be mobile.

Keep the questions coming.

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