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Bought a superstar. Did I make a mistake?

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#1 richard hoyt

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Posted 18 January 2013 - 09:56 PM

I have been looking at autoguiders for a little while and was looking at the st-i and the lodestar. I talked to a couple of stores and decided on the lodestar. In speaking with store I bought from he also mentioned the superstar. He indicated that it wasn't as sensitive but close enough not to be a big deal. I was intrigued with the bigger sensor and color for a planetary camera. After talking with others I am getting the impression that I shouldn't have bought this. I was able to get it for the same price as the lodestar and I can return it if need be. Any advice?

#2 korborh

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Posted 18 January 2013 - 10:21 PM

Just for auto-guiding, I think the specs for superstar are better than lodestar.
The chip is less noisy, it has smaller square pixels (good for both short FL bin1 and long FL bin2), does not suffer from interlacing (which can really mess up centroid) and is very sensitive.

Look at these images: http://www.sxccd.com...tar_comparison/

However if you got this for any kind of planetary work, then you made a mistake and will be disappointed because superstar has a very low frame rate (1.6 fps). I have no idea why SX advertises it as planetary camera.

BTW, the sensor size is same for lodestar and superstar. Superstar has higher pixel count with smaller pixels.

#3 Footbag

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Posted 18 January 2013 - 10:43 PM

Wow, now korborh has me thinking. I would expect the lodestar to be better for longer FL guiding and the superstar better for piggyback guiding. I didn't know you could bin the superstar. Can you bin in PHD?

I also hadn't noticed Interlacing problems with others images, and hadn't considered that. But, an OAG requires the most sensitive of guide cameras, and the lodestar seems to be the most recomended. Maybe because the superstar is so new?

If you purchased the color version, though, it wont be as sensitive as mono. That means fewer guide stars. I also think it effects binning somehow as well.

#4 Peter in Reno

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Posted 18 January 2013 - 11:19 PM

Terry Platt posted a comparison image taken with Lodestar and SuperStar and it appears that Lodestar is more sensitive than SuperStarat bin 1x1 and probably slightly more sensitive than SuperStar when Lodestar is binned 1x1 and SuperStar at binned 2x2. For auto guiding only purpose I would still prefer Lodestar due to high sensitivity especially when using OAG.

No you cannot bin with PHD unfortunately but it's not a total loss since Lodestar is still extremely sensitive at binned 1x1. You can bin Lodestar with Maxim but I don't use Maxim and I have very good experience with Lodestar binned at 1x1 and PHD.

That's my IMHO.

Peter

#5 korborh

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Posted 18 January 2013 - 11:49 PM

The chip in superstar ICX205 is quite sensitive and looking at Terry's images I cannot conclude if bin1 lodestar is brighter than bin2 Superstar. One can bin in Maxim (not sure about PHD).
To try out interlacing effect, take several short exposures 1sec or less of a star in focus and analyze them for the star profile. If you see a alternating bright/dark effect, that is due to interlacing. It can throw off the centroid. The chip in lodestar is interlaced but the one in superstar is not.
Only the fps of superstar is quite bad - 1.6 fps. I think its also too expensive for a un-cooled guide camera.

#6 richard hoyt

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Posted 19 January 2013 - 02:32 AM

@ korborh

thanks for the info, i didn't get it specifically for a planetary imager. Just thought it would be a neat bonus. what software do you guys use for guiding, this is my first time with a guider so I am a little lost with figuring the software out. So far i have the software that came with the guider and just downloaded PHD. Maxim seemed to be really pricey so i don't think I am going to get that.

Do you know of any good tutorials on the guiding software? I searched a little and didn't really find anything really useful.

thanks again.

#7 korborh

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Posted 19 January 2013 - 12:29 PM

For autoguiding you really want a mono camera.
I am using MaxImDL for guiding and have used PHD before. MaxImDL is very costly, and is needed if you need any automation. But there are free autoguding apps you can use.
Note that for the lodestar, SX recommends using bin2 for guiding to reduce the interlacing artifacts. This makes the already large pixels of lodestar much bigger and not optimum for long FL.

You can google "craig stark autoguiding" for resources on autoguiding. I do not know of any tutorials. I would recommend read through these forums and try your own techniques to learn from your experience. It will be easier to get started using a small guide-scope to autoguide a short FL refractor.

#8 Peter in Reno

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Posted 19 January 2013 - 01:13 PM

I have not seen one report about people owning SuperStar for autoguiding so no one can make a claim that SuperStar can actually do a better job than Lodestar. Terry's comparison images with Lodestar and SuperStar shows that Lodestar is significantly more sensitive than SuperStar.

I use Lodestar with PHD and never ever had interlacing issues. The interlacing issues I've heard is most likely a bug in Maxim. It was reported somewhere in SX Yahoo Groups by Terry but I can't find it because it was a while ago. Maxim said to bin Lodestar to make it work. That's a terrible suggestion because Lodestar already has fairly large pixels. Why can't Maxim fix it? Maybe they already did, I don't know.

Bottom line, not only I say that Lodestar is one of the best autoguider due to extreme high sensitivity, so did many others. Search in this and other forums and you will see many positive reports or claims about Lodestar's autoguiding capability.

Until I see actual data or reports about SuperStar, I highly recommend Lodestar over SuperStar for autoguiding. I can't make a recommendation for other purposes like planetary imaging.

Peter

#9 korborh

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Posted 19 January 2013 - 03:56 PM

I am not saying Lodestar is bad or anything. However there being Superstar, the comparison is interesting. Superstar does not have much user feedback. So not many reports on its performance, which makes the decision difficult especially given its high price.

Interlacing is not a Maxim specific issue. It is a characteristic of the CCD hardware itself in how it is read. An interlaced chip will read odd and even lines separately, so nothing Maxim/PHD can do read full frame in one go. You don't see it in PHD because PHD does not give detail view of the star to analyze it closely (like zooming in, stretch and 3D profile). When seeing is not good, try 0.5sec guide exposures (bin1) in MaximDL zoomed in view of the guidestar and plot a running 3-D profile. I think the 'fixes' Maxim added must be some interlacing algorithms or interpolation to reduce the effect. These will have to be turned off to the see full effect of interlacing.

Again, its not the fault of Maxim that it shows more detail on the guide star to see interlacing artifacts.
Lodestar is a good guide camera , but I wanted to bring up some of its limitations, which are not mentioned often.

#10 Midnight Dan

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Posted 20 January 2013 - 11:37 AM

I've been giving some thought to upgrading my guider from an SSAG to something better. I've taken a look at a lot of specs and the three that stand out are the Lodestar, Superstar, and Orion SS 3G:

Posted Image

The Superstar has pixels roughly half the size of the Lodestar so a good comparison would be 2x2 binned Superstar vs. Lodestar. I think you can multiply the gain by the number of pixels binned (?) so looked at that way, the gain of the Superstar sensor comes out to 1.2 vs 0.9 for the Lodestar so it would seem to be a little more sensitive when binned. This *seems* to agree with Terry's test, but it's hard to tell which image shows more sensitivity. But to be honest, the specs of the two are similar enough that I don't think it really matters. The only significant difference in the specs is the download time for the Superstar which is 3x the Lodestar due to the higher pixel count.

The Orion SS G3 is an interesting option. It's $150 to $200 less expensive than the other two, and has similar specs. It achieves a much lower dark current but that is due to the active cooling. The dark current is low enough in all of these that it really would only make a difference in very long exposures, which is not what you're looking for in guiding anyway. On the other hand, it allows you to use it as a monochrome long exposure imager too. Of course, the cooling adds a lot of weight and bulk to this camera too.

Seems like for just guiding, the Lodestar or the Superstar 2x2 binned are good choices. They're small and lightweight and offer good sensitivity. The SS G3 can save me some money and provide long exposure imaging, but at the expense of weight and size and another cable for cooling power.

Decisions, decisions. I'm leaning towards the Lodestar but still mulling it over.

-Dan

#11 korborh

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Posted 20 January 2013 - 12:44 PM

The lodestar/superstar are only attractive for their 1.25" barrel design and if you really need that for your setup to work. Otherwise there are similarly sensitive and much cheaper options out there.

I decided to go with used DSI II pro mono - the flat camera shape with USB cable coming from side works better in my OAG/scope setup. I already have the same size DSI I pro setup this way so I can keep the same working setup with the upgrade.

#12 groz

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Posted 20 January 2013 - 02:10 PM

As far as sensativity goes, the sensativity of any single pixel is directly proportional to the surface area of the silicon for that pixel. Superstar pixels are 4.5 x 4.5, while lodestar pixels are 8.2 x 8.4. To get a decent comparison of sensativity then, you need to use a binned superstar beside an unbinned lodestar, ending up with roughly equivalent pixel sizes. As soon as you bin the superstar, the pixel count for frame downloads, will go down by a factor of 4, so potential frame rates, go up by a factor of 4. Doesn't really make any difference tho, if your guide exposures are going to be longer than the download period. You will still be limited by exposure time, not download time.

Using an example of the ubiquitous ST80 for a telescope, it's possible to compare the fields of the two. The lodestar would give a field of 52x42 arcminutes, pixel resolution of 4.2 arcseconds per pixel, slightly longer in the other direction because lodestar pixels are not square. Superstar in the same telescope, gives a field of 53x39, pixel resolution of 2.32 arcseconds per pixel. If you bin it, resolution goes up to 5.6 arcseconds per pixel. For comparison, a qhy5/ssag/costar (all the same sensor) in the same telescope, results in a field of 57x45, pixel resolution of 2.7 arcseconds per pixel.

Where the superstar can absolutely shine, is when you go to much shorter focal lenghts for guiding. We currently use qhy5 in a 9x50, which gives a field of 128x102 arcminutes, HUGE. But, where this combination lacks, is in sensativity and resolution. The resulting resolution is 6.08 arcseconds per pixel. Put a superstar into the same configuration, you get a field of 120x88, but, it delivers 16 bit data instead of 8 bit, with 5.2 arcsecond pixels. So there is a huge win in terms of data quality, and a decent win in terms of resolution with the Superstar.

The way I see it, if you want high sensativity etc, bin the superstar, and you will get performance on par with a lodestar. If you want high resolution, run the superstar unbinned, to get the increase in resolution. If you want resolution and framerate, then use software that'll do subframe downloads, and give you the frame rates you want, on the area in question from the superstar.

My wife and I have upgraded telescopes over the last few months, and, will be starting on camera gear next. First on the agenda will be our guiding systems. I'm not even going to consider anything based on the mt9m001 chips, we already have that. For us, the decision is lodestar vs superstar, and, in my mind, that's a no brainer. Superstar is far more flexible, and, when you do the apples to apples comparison (binned superstar vs unbinned lodestar), they should have equivalent performance. But, the smaller pixels available in the superstar, open up avenues that have not been available before.

We will likely get our first one, in a couple of months, then I can give it a good test run, and determine if my math on the differences is correct, but right now I am fairly convinced, that a superstar in a very short focal length will outperform the qhy5 in the same setup, by a long shot. Superstar gives us the option to do that, lodestar does not. And, when we put it into an oag on the long focal length setup, binned, the superstar should perform just as well as the lodestar.

#13 Footbag

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Posted 20 January 2013 - 08:24 PM

I can see the superstar begin very good for short focal length guiding setups. Or as a digital finderscope. It will be interesting when reviews begin to come in.

But, a lot of people are using PHD. If you cannot bin with PHD, then you're dealing with small pixels. It seems like all of the people advocating the lodestar are using OAG's. I'm wondering if the unbinned superstar would be sensitive enough for an OAG.

#14 wolfman_4_ever

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Posted 22 January 2013 - 12:12 AM

I've only seen the interlace issue when I force the lodestar (through Maxim) to Bin 3x for testing purposes.

I have 2 lodestars and have tried guiding in SBS with a short refractor and the AO at the same time. The AO would eventually max out on movement because the star moved too far using the short focal length refractor, pixels and PHD for guiding. The AO was only set to move the AO glass and not the mount through Maxim.

I do bin 4x using OAG and AO sometimes. I set my trackbox to 4x and set my allowable pixel movement to 1. I can guide for hours in either 2x or 4x binning using AO, OAG and HD11 with .7x reducer with a .1 RMS error. (AO RMS)

#15 korborh

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Posted 22 January 2013 - 12:53 AM

Dave, how short are your guide exposures?

#16 wolfman_4_ever

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Posted 22 January 2013 - 01:45 AM

For the AO or when using the guide scope?

I try to keep the AO under .5 sec. Ideally somewhere in the 100ths is best. And 100ths will require a bright star. And a trackbox that small too..

Guide scope, it all depends on what I am doing.. no more than (usually) 2 sec, but no less than .5 sec.

#17 rainycityastro

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Posted 23 January 2013 - 06:20 PM

No you cannot bin with PHD unfortunately but it's not a total loss since Lodestar is still extremely sensitive at binned 1x1.

Actually you can bin using PhD. I do it all the time with my superstar. You need to use ASCOM camera and have the appropriate ASCOM driver that can do binning. Brett McKee has developed a driver that does what you need. Check out the sx ascom yahoo group for more details.

#18 wolfman_4_ever

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Posted 27 January 2013 - 04:20 AM

Thanks for the advice! Should help a bunch.






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