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Observing >> Variable Star Observing and Radio Astronomy

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KenSikes
member


Reged: 01/17/10

SSP-3A new
      #5771543 - 04/01/13 07:40 PM

I am awaiting the delivery of a SSP-3A photodiode photometer within the next few days. Is there anyone else on this forum that has any experience using the SSP-3A or is interested in this photometer.

Thanks
Ken Sikes


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Pat Rochford
member
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Reged: 09/30/08

Re: SSP-3A new [Re: KenSikes]
      #5771686 - 04/01/13 08:58 PM

No experience with the SSP-3A, but the SSP-5 I bought was the best move I'd made in over a decade. After years of dealing with the frustrations of using a CCD camera for science, I've stepped backward a bit in technology, but stepped up ten-fold, my ability to produce consistent and very accurate data. Too bad I didn't discover this a long time ago.

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rutherfordt
sage
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Reged: 05/07/06

Loc: Northeast Tennessee USA
Re: SSP-3A new [Re: KenSikes]
      #5772336 - 04/02/13 08:42 AM

Ken:

I have an SSP-4 (its the infrared one). I really enjoy using it. There is a bit of a curve to learning how to transform your data to the standard system, but nothing too bad.

Tom


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KenSikes
member


Reged: 01/17/10

Re: SSP-3A new [Re: rutherfordt]
      #5773710 - 04/02/13 07:05 PM

Pat, Tom
It's good to know that there is still a need for the PEP equipment. The SSP3A comes with a data reducing program as an extra add-on. I also have the Henden-Kaitchuck book that is very dog eared on key equations for data reduction.

I am hoping that more will become PEP observers as well. I have found a wealth of knowledge on the AAVSO website and look forward to shareing information with others.

I know that many are doing photometry with CCD, but the data harvesting in this mannor does not allow one to follow a single star as PEP does, and the CCD's don't work very well on brighter stars.

What project stars are you working ?

Ken


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Pat Rochford
member
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Reged: 09/30/08

Re: SSP-3A new [Re: KenSikes]
      #5774385 - 04/02/13 11:05 PM

Ken,

I am presently monitoring about 75 of the AAVSO PEP program stars. The SSP-5 is quite a bit more sensitive than the 3, and when combined with a 14" SCT, stars brighter than about magnitude 5.5 "peg the meter" so to speak. Still, these 6th to 8th mag low amplitude guys are keeping me plenty busy. As I get more familiar with using this, perhaps I might venture into some other areas as well.

I don't use the data reduction program though. Pen and paper at the telescope, average the readings with a small calculator attached to my clip board and then upload the numbers to AAVSO's PEPObs page the next day. It couldn't be much simpler and really fits my mostly low-tech style.

I made plane reservations this evening to attend the spring meeting of AAVSO in Boone, NC in May. Hoping to meet up with a few old farts like myself who are using PEP's.


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rutherfordt
sage
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Reged: 05/07/06

Loc: Northeast Tennessee USA
Re: SSP-3A new [Re: KenSikes]
      #5775371 - 04/03/13 11:43 AM

I am currently following epsilon Aurigae-- I started in late 2008 (before the eclipse), followed it through the eclipse, and am now getting post-eclipse data (bad weather this past winter so not too many data points). I have also gotten some data on Betelgeuse-- its really bright in the IR!

The SSP-4 is not as sensitive as either the SSP-3 or the SSP-5. I am using an 8-inch SCT and am limited to targets brighter than mag 2 (infrared mag 2, not visual mag 2). I have a 10-inch SCT that I am trying to get into service so that should increase my capabilities in the future.

Boone is just across the mountains from me, about a 90-minute drive so I am giving some thought to attending the AAVSO meeting as well.

Tom


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KenSikes
member


Reged: 01/17/10

Re: SSP-3A new [Re: rutherfordt]
      #5776131 - 04/03/13 06:23 PM

Tom,
Jeff Hopkins also has a SSP4 and as I remember he sent his back To Optec and had a different detector installed and was an improvement. Here is a link to his site
http://www.hposoft.com/Astro/IR.html

Ken


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KenSikes
member


Reged: 01/17/10

Re: SSP-3A new [Re: Pat Rochford]
      #5776142 - 04/03/13 06:29 PM

Back in the late 1970's a friend gave me a home made photometer with a 931A tube to use. I latter replaced the tube with a 1P21. still have both tubes but no power supply or amplifier to use the photometer.

I would have liked to purchase a SSP5, but did not have the extra $$$ for it,just the SSP3a...maybe at a latter date. There are many stars that the SSP3a can be used on. PEP is not as dead as I thought..

Ken


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Pat Rochford
member
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Reged: 09/30/08

Re: SSP-3A new [Re: KenSikes]
      #5776585 - 04/03/13 09:58 PM

I would have liked to purchase a SSP5, but did not have the extra $$$ for it,just the SSP3a...maybe at a latter date. There are many stars that the SSP3a can be used on. PEP is not as dead as I thought..




Ken - I was fortunate enough to find my SSP-5 on AM for less than $1500 ... a real stroke of luck. It had just been upgraded with the generation 2 electronics. It looks and works like a new unit.


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Pat Rochford
member
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Reged: 09/30/08

Re: SSP-3A new [Re: Pat Rochford]
      #5776587 - 04/03/13 10:00 PM

Quote:

I would have liked to purchase a SSP5, but did not have the extra $$$ for it,just the SSP3a...maybe at a latter date. There are many stars that the SSP3a can be used on. PEP is not as dead as I thought..
Quote:




Ken - I was fortunate enough to find my SSP-5 on AM for less than $1500 ... a real stroke of luck. It had just been upgraded with the generation 2 electronics. It looks and works like a new unit.




Edited by Pat Rochford (04/03/13 10:01 PM)


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rutherfordt
sage
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Reged: 05/07/06

Loc: Northeast Tennessee USA
Re: SSP-3A new [Re: KenSikes]
      #5777147 - 04/04/13 08:08 AM

Ken:

The upgrade that Hopkins did was to change the 0.3mm detector to the 1mm detector, which is the one that I have-- it doesn't do anything about the sensitivity. There just aren't many infrared photons coming in from most stars. One nice advantage of the infrared, though is that there is almost no light pollution-- the night sky is black in the infrared. I could even collect data from a mall parking lot if I needed to.

The SSP-4 is different from the other SSP's in that it is thermoelectrically cooled. I typically have it running at -40 C (below ambient). This does mean that I am tied to a power supply, but that isn't really a problem.


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KenSikes
member


Reged: 01/17/10

Re: SSP-3A new [Re: KenSikes]
      #5816292 - 04/22/13 08:28 PM

My SSP3a arrived last week and I spent Saturday night working with it in the back yard. I must say I am impressed with the quality of work that Optec put into the photometer. I hope to be up and running in the next couple of weeks.

Ken Sikes


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Pat Rochford
member
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Reged: 09/30/08

Re: SSP-3A new [Re: KenSikes]
      #5816523 - 04/22/13 10:53 PM

My thoughts exactly when I received my second hand SSP-5.

I've called Optec on more than one occasion with questions, and have been treated with the same care and respect as if I'd purchased it new. A first class company that will definitely get my business in the future.


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ASTERON
Carpal Tunnel
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Reged: 11/24/07

Loc: ISRAEL
Re: SSP-3A new [Re: Pat Rochford]
      #5820054 - 04/24/13 03:33 PM

Hello everybody,
Would you care on elaborating what are the advantages /disadvantages of using a Photodiode Photometer versus CCD for monitoring Variable stars and SN ?
I was under the impression that Photodiodes were obsolete. Obviously, I was wrong.
I would really like to know the difference and Pros and Cons of Using one or the other for precision photometry.
Thanks

Edited by ASTERON (04/24/13 03:34 PM)


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StupendousMan
super member


Reged: 08/21/05

Re: SSP-3A new [Re: ASTERON]
      #5820763 - 04/24/13 08:32 PM

Photoelectric detectors can provide higher precision than CCDs, in the right circumstances. If you want to measure just a few objects, and each target has a star of similar brightness and color just a degree or two away, then a series of back-and-forth measurements with the photometer will beat a series of measurements with a CCD. The photometer has lower readout noise, and one doesn't have to take such care with flatfielding.

On the other hand, if you are interested in measurements of many stars in a small field, the CCD will let you measure them all at once. Big win for the CCD in that situation. It's also much simpler to put a target object onto the field of a CCD than into the small active area of a photometer.


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brianb11213
Postmaster
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Reged: 02/25/09

Loc: 55.215N 6.554W
Re: SSP-3A new [Re: StupendousMan]
      #5821126 - 04/25/13 12:09 AM

Quote:

Photoelectric detectors can provide higher precision than CCDs, in the right circumstances. If you want to measure just a few objects, and each target has a star of similar brightness and color just a degree or two away, then a series of back-and-forth measurements with the photometer will beat a series of measurements with a CCD. The photometer has lower readout noise, and one doesn't have to take such care with flatfielding.

On the other hand, if you are interested in measurements of many stars in a small field, the CCD will let you measure them all at once. Big win for the CCD in that situation. It's also much simpler to put a target object onto the field of a CCD than into the small active area of a photometer.



Also remember that the PEP has a need for a great many photons than CCD: the working range for estimates with any given instruments is almost 10 magnitudes deeper with a CCD.


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ASTERON
Carpal Tunnel
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Reged: 11/24/07

Loc: ISRAEL
Re: SSP-3A new [Re: brianb11213]
      #5821426 - 04/25/13 07:51 AM

Stupendousman and Brianb, thank you both for your answers.

So the only advantages of a PEP is the lower reading noise and lack of need for flatfielding ?
How low is the reading noise in a good Photodiode photometer as compared to a good modern CCD ( Such as a Sony HAD like the recent ones ?)
What is the QE of the Photodiode as compared to a Large pixel on a good CCD ?

Finally, How long do you need to expose the Photodiode to get a satisfactory reading as compared to a more sensitive CCD pixel (I am interested in the ratio of exposure times and not in an absolute number, as obviously the exposure length will also depend on the target's magnitude.)
Thanks

Edited by ASTERON (04/25/13 07:53 AM)


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rutherfordt
sage
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Reged: 05/07/06

Loc: Northeast Tennessee USA
Re: SSP-3A new [Re: ASTERON]
      #5821559 - 04/25/13 09:19 AM

With the SSP-4 that I use, the control software allows me to take 4 10-second "exposures," giving me a total collection time of 40 seconds. Then move to the nearby sky and do it again, then to your comp star and do it again, then the sky beside the comp star and do it again. Repeat this procedure two more times, average the results, and you will now have one data point for that star that night. PEP is very time intensive compared to CCD observations, but it is the only way to monitor bright stars that will saturate a CCD.

Tom


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StupendousMan
super member


Reged: 08/21/05

Re: SSP-3A [Re: rutherfordt]
      #5828771 - 04/28/13 05:08 PM

A good photoelectric photometer has a quantum efficiency which is considerably lower than that of a CCD - perhaps 20 to 25 percent for the photometer, versus 70-90 percent for a top-of-the-line back-illuminated CCD.

On the other hand, the readout noise of a photometer is very low, effectively zero for many purposes.


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KenSikes
member


Reged: 01/17/10

Re: SSP-3A new [Re: StupendousMan]
      #5902229 - 06/04/13 05:21 PM

What is the norm on selecting Transformation stars...since many of the stars that Johnson used are double stars, are they ok to use ?

Ken Sikes


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