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Astrophotography and Sketching >> DSLR & Digital Camera Astro Imaging & Processing

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mmalik
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Lodestar Autoguider
      #5450486 - 10/01/12 05:05 PM Attachment (172 downloads)

I just got Lodestar Autoguider... camera; here is 5sec shot via PHD with lens cap on. Are these dead pixels or what? I tried different caps with same result. Shouldn't new camera have zero dead pixels if that's what they are?

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mmalik
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Re: LodeStar Autoguider new [Re: mmalik]
      #5450499 - 10/01/12 05:17 PM Attachment (53 downloads)

Sensor of the camera, which looks clean.

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David PavlichAdministrator
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Re: Lodestar Autoguider new [Re: mmalik]
      #5450614 - 10/01/12 06:29 PM

Probably hot pixels and it's normal.

David


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guyroch
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Re: Lodestar Autoguider new [Re: David Pavlich]
      #5450624 - 10/01/12 06:34 PM

Looks like hot pixels. New or old _all_ sensors have defects. I don;t think I have that many on my lodestar but I always take PHD darks so I wouldn't know.

If you take darks (in PHD) they should disappear.

Guylain


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mmalik
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Re: Lodestar Autoguider new [Re: guyroch]
      #5450716 - 10/01/12 07:40 PM Attachment (103 downloads)

Here is a 5sec dark taken with PHD; looks the same to me.

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mmalik
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Re: Lodestar Autoguider new [Re: guyroch]
      #5450743 - 10/01/12 07:57 PM

Let me take a dark with colder temp at night; will post results. Thx

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Alex McConahay
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Re: Lodestar Autoguider new [Re: mmalik]
      #5450853 - 10/01/12 08:57 PM

It is possible to get chips with nearly no defects. But they cost a whole whole lot more than those found in cameras for regular human beings. Chips are graded as to how many hot pixels and other "defects" they have. We average consumers do not get the top frade.

These hot pixels will not at all affect your guiding because allost any start will be quite a bit more substantial than these pixels.

Alex


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fetoma
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Re: Lodestar Autoguider new [Re: Alex McConahay]
      #5450915 - 10/01/12 09:33 PM

Maybe ask Terry on the SX Yahoo group?

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guyroch
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Re: Lodestar Autoguider new [Re: mmalik]
      #5450931 - 10/01/12 09:45 PM

Quote:

Here is a 5sec dark taken with PHD; looks the same to me.




That's the point. Now let PHD subtract those hot pixels on each frame it takes a frame for guiding. As long as you keep the same exposure length guiding that you did when you took your PHD dark frame PHD will use it and subtract it.

Hope this helps.

Guylain


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mmalik
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Re: Lodestar Autoguider new [Re: guyroch]
      #5451038 - 10/01/12 10:47 PM Attachment (44 downloads)

Quote:

That's the point. Now let PHD subtract those hot pixels on each frame it takes a frame for guiding. As long as you keep the same exposure length guiding that you did when you took your PHD dark frame PHD will use it and subtract it.




I have never taken dark frames when guiding; explain it a bit for me. So I take a dark (of equal length), save it and then load it into PHD before guiding? Or do I just take dark (of equal length) and just start guiding right away? If not saved, is it held in PHD cache somewhere?

Here is a 5sec dark frame I took with relatively cold camera.


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nwinston
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Re: Lodestar Autoguider new [Re: mmalik]
      #5451063 - 10/01/12 11:01 PM

To take a dark frame in PHD, all you need to do is put the cap on your guide scope and press the "Take Dark" button in the bottom of the window. Make sure the selected exposure is the one you will be using for guiding. The program will automatically subtract the dark frame from the rest of the exposures.

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Re: Lodestar Autoguider new [Re: nwinston]
      #5451066 - 10/01/12 11:02 PM

You just have to do it before you start "capture"

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Re: Lodestar Autoguider new [Re: Nils_Lars]
      #5451089 - 10/01/12 11:16 PM

like everyone said... it's right there in PHD.

Look in the lower right corner in PHD, there is a button there to take darks. Press on it, put the cap on, and let PHD take a few darks... it takes 5 actually. Then PHD will apply the master dark to each guide frames and the noise / bad pixels will be removed and you'll be left with clean frames to guide with.

Hope this helps,

Guylain


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mmalik
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Re: Lodestar Autoguider new [Re: guyroch]
      #5451182 - 10/02/12 12:11 AM

I know where the button is; I meant do I need to save in PHD and load the dark in PHD or does PHD saves it in cache?

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Re: Lodestar Autoguider new [Re: mmalik]
      #5451207 - 10/02/12 12:30 AM

Quote:

I know where the button is; I meant do I need to save in PHD and load the dark in PHD or does PHD saves it in cache?




LOL. It's saved in PHD's memory. It's good for your active session... or until you change guide exposure length. If you turn PHD off and on again you need to takes your darks again. Fortunately it only takes 5 seconds.

Guylain


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Re: Lodestar Autoguider new [Re: guyroch]
      #5451957 - 10/02/12 01:21 PM

PHD does it all for you. It's easier then you are thinking.

I don't have a Lodestar, but will probably be getting one soon. There may be slightly more hot pixels then I would've expected, but who cares about that. It's a guide camera. The sensitivity of it may be the reason for more hot pixels.

Like others have said, take the darks in PHD and apply them then point up and you will know whether it's working. You should see at least a few obvious stars.


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mmalik
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Re: Lodestar Autoguider new [Re: Footbag]
      #5452426 - 10/02/12 06:32 PM Attachment (102 downloads)

Thanks everyone for your feedback.

I am using a 4" Orion APO as a guide scope. Below is 1sec light frame I took via PHD through the guide scope (Image is M35). Notice stars a oblong; and I am not sure what's causing it. It all can't be flexure because if you notice all of my darks had oblong hot/dead pixels. Anyway, PHD couldn't guide and kept alarming on decent mid-range stars in this field. I made sure I wasn't guiding on too bright or too dim stars. Long story short, first real test of this camera with this particular setup has been a failure.

I do feel this particular camera has these oblong shaped hot/dead pixels which is odd; I would have expected some but not all defects to be oblong. Also notice, the image is hazy; I never could bring stars to crisper focus besides being oblong. Your suggestions/solutions are welcome before I send it back. Thanks again for all the help!

Note: I have done quite a bit of guiding with this setup via SSAG 1.5 MP and never had a problem; stars have been crisp and round, although Lodestar shows more stars in a given field given the sensitivity/spec difference.

Note: I have brightened image a bit for better visualization.


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Re: Lodestar Autoguider new [Re: mmalik]
      #5452503 - 10/02/12 07:17 PM

a short exposure should not really be subject to flexure problems, and anyway, differential flexure does not even enter the picture here unless you were guiding with the main scope and imaging through the guide scope. so the star shape is most likely caused by your camera not being square with the optics, or maybe just poor optics.

PhD should have no problem at all guiding on that image. guide stars do not even have to be round or even particularly well focused for PhD to work properly. you should see the star images coming off of my OAG right now - they look like seagulls.

PhD is probably mad about the star mass, or perhaps saturated stars. although saturated stars seem unlikely with the 16-bit resolution of this camera. unless you tell us the error, we can't help.

if you don't like the lodestar, send it to me because there's nothing wrong with it.


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mmalik
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Re: Lodestar Autoguider new [Re: pfile]
      #5452637 - 10/02/12 08:57 PM

No error; PHD just keeps losing track of the star with usual alarm/sound output.

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Re: Lodestar Autoguider new [Re: mmalik]
      #5452799 - 10/02/12 10:39 PM

This is almost always the case of a low SNR. Can you please provide a print screen of your PHD when this occurs. I'm curious to see the guide frame luminosity as a whole. You might be guiding to long or to short combined with the slider that changes the luminosity in PHD.

Guylain


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Re: Lodestar Autoguider new [Re: mmalik]
      #5452930 - 10/03/12 12:17 AM

Mike - you don't want the stars to be sharp pinpoints - Phd can guide more accurately if the stars are a bit out of focus. Bu having the image out of focus, the light from a star is spread over many pixels. Phd uses this information to more accurately calculate the center of mass of the guide star. This allows Phd to do sub-pixel accuracy guiding. This is also why its not an issue if the guide star isn't round - Phd is only calculating the center of mass for the guidestar.

My ONAG guider gives me guidestars that are actually donuts. Even though the guidestar is CLEARLY out of focus, I'm guiding right now at about 1/2 arcsec accuracy (RMS).

As far as the alarming - I'm not sure if this is the problem, but the field you have with M35 could be difficult to isolate a good guide star. Many of the bright stars you might choose for guiding are very close to another bright star (and even some not so bright stars). Is it possible that your alarming is coming from Phd picking up another star wandering into the guide box?


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Re: Lodestar Autoguider new [Re: srosenfraz]
      #5452950 - 10/03/12 12:39 AM

if that's the case then he can reduce the guide exposure length, or maybe make the search box smaller.

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Re: Lodestar Autoguider new [Re: mmalik]
      #5453188 - 10/03/12 08:19 AM

Quote:

Thanks everyone for your feedback.

I am using a 4" Orion APO as a guide scope. Below is 1sec light frame I took via PHD through the guide scope (Image is M35). Notice stars a oblong; and I am not sure what's causing it. It all can't be flexure because if you notice all of my darks had oblong hot/dead pixels. Anyway, PHD couldn't guide and kept alarming on decent mid-range stars in this field. I made sure I wasn't guiding on too bright or too dim stars. Long story short, first real test of this camera with this particular setup has been a failure.

I do feel this particular camera has these oblong shaped hot/dead pixels which is odd; I would have expected some but not all defects to be oblong. Also notice, the image is hazy; I never could bring stars to crisper focus besides being oblong. Your suggestions/solutions are welcome before I send it back. Thanks again for all the help!

Note: I have done quite a bit of guiding with this setup via SSAG 1.5 MP and never had a problem; stars have been crisp and round, although Lodestar shows more stars in a given field given the sensitivity/spec difference.

Note: I have brightened image a bit for better visualization.





This picture really makes me want a Lodestar. I typically have no more then 4 stars in my field.

Until you said you were losing stars, I though maybe it has to do with you specific star selsction. Too bright or too dim, etc... But I had one problem with my SSAG that exhibited behavior like you are seeing. The St-4 cable became unseated from the mount. Everything worked fine until it was time to calibrate. Maybe given the poor connector on the Lodastar, that has something to do with it.


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mmalik
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Re: Lodestar Autoguider new [Re: srosenfraz]
      #5453242 - 10/03/12 09:11 AM

Quote:

Is it possible that your alarming is coming from PHD picking up another star wandering into the guide box?




Scott, you may be right; will try another test soon on a different target.

On a side note, I wanted to ask folks what their thoughts are about SBIG's ST-i monochrome autoguider; has anyone used it? How does ST-i monochrome autoguider compare to Lodestar autoguider?


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Alex McConahay
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Re: Lodestar Autoguider new [Re: Footbag]
      #5453248 - 10/03/12 09:15 AM

That picture had a lot more stars than I usually get in a field of view in my off axis guider. So, unless you are using a full separate scope, I would not buy a Lodestar based on that picture alone.

I have actually done some studies with Starshooter, Image Source, and Lodestar, and did find the Lodestar pulled in more stars. But the difference was not so great as that picture would lead one to believe.

Alex


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MPT
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Re: Lodestar Autoguider new [Re: srosenfraz]
      #5453473 - 10/03/12 12:12 PM

Quote:

Mike - you don't want the stars to be sharp pinpoints - Phd can guide more accurately if the stars are a bit out of focus. Bu having the image out of focus, the light from a star is spread over many pixels. Phd uses this information to more accurately calculate the center of mass of the guide star. This allows Phd to do sub-pixel accuracy guiding. This is also why its not an issue if the guide star isn't round - Phd is only calculating the center of mass for the guidestar.





Hey Mike, I wanted to second this suggestion as well. I've noticed much better results tracking while a tad bit out of focus. Also, I agree with a couple of other suggestions here, I would turn down the exposure time a little bit.

I've been browsing around for a double duty autoguider as well...these images are making me really like the lodestar.


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mmalik
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Re: Lodestar Autoguider new [Re: Footbag]
      #5453744 - 10/03/12 03:40 PM Attachment (41 downloads)

Quote:

Maybe given the poor connector on the Lodestar, that has something to do with it.




ST-4 connector wasn't the problem in my case; but you bring up a good point. ST-4 port on the back of Lodestar doesn't have a lock like typical ST-4 port (or any phone port) does. Here is a comparison of the ST-4 connectors for both Lodestar and SBIG's ST-i. I like standard ST-4 port rather than the miniaturized one on Lodestar.

Since I had a standard ST-4 cable already running through the mount, I tried this... 6-pin inline coupler without much luck; not sure why? I ended up connecting Lodestar directly to the mount.


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mmalik
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Re: Lodestar Autoguider new [Re: mmalik]
      #5474410 - 10/17/12 02:19 AM Attachment (57 downloads)

Update: I ended up sending my Lodestar Autoguider back due to elongated looking hot pixels I have stated/imaged above. Following is a 5sec dark taken through a friend's lodestar autoguider for comparison which looks much better than mine.

I ended up getting SBIG ST-i monochrome autoguider whose details will follow in next posts.


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mmalik
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Re: Lodestar Autoguider new [Re: mmalik]
      #5474412 - 10/17/12 02:22 AM Attachment (81 downloads)

Few pics of SBIG ST-i monochrome autoguider I just bought:

Front:


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mmalik
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Re: Lodestar Autoguider new [Re: mmalik]
      #5474414 - 10/17/12 02:23 AM Attachment (49 downloads)

Back:

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mmalik
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Re: Lodestar Autoguider new [Re: mmalik]
      #5474425 - 10/17/12 02:36 AM Attachment (57 downloads)

1sec dark through ST-i @70F:

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mmalik
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Re: Lodestar Autoguider new [Re: mmalik]
      #5474428 - 10/17/12 02:41 AM

To sum up, my quest for a decent autoguider has ended up at SBIG ST-i monochrome which seems to have NO column defects or dead pixels or elongated hot pixels, etc. I have tested ST-i and it works great. My first ST-i guided pic is posted here...

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Re: Lodestar Autoguider new [Re: mmalik]
      #5476911 - 10/18/12 12:54 PM

Hi Mike - out of curiosity, I see that you posted a 5 second dark with your Lodestar as well as a better looking one with your friend's Lodestar. However, your dark frame from the ST-i was only 1 second. When you have a chance, would you mind posting a 5 second dark from the ST-i? I'm curious to see a direct comparison to the Lodestar frames. Also, do you have any idea what the ambient temps were when each of these dark frames was captured?

Thanks!


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mmalik
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Re: Lodestar Autoguider new [Re: srosenfraz]
      #5477304 - 10/18/12 04:07 PM Attachment (53 downloads)

Scott, here the temp/other details:

•Steve's 5sec Lodestar image I "think" was taken at much lower temp outdoors (~40F)
•My ST-i 1sec was taken indoors at around 70F
•Below is ST-i 5sec dark taken indoors at around 70F

Note: All images are stretched images; developed in IP5

Although I bought ST-i (and prior Lodestar) mainly for guiding, I am bit particular about sensor quality though given I might use it for casual planetary imaging sometime. I do understand, one doesn't need any quality for guiding given it will guide on any blobby looking thing, but that's not the point. A camera at $600 needs to have some sense of quality and ST-i offers that while Lodestar completely disregards that with column and other defects.

If I get an opportunity, I'll post outdoor low temp 5sec dark sometime of ST-i.


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Re: Lodestar Autoguider new [Re: mmalik]
      #5477384 - 10/18/12 04:51 PM

Thanks for posting that, Mike. That's a very clean looking dark for 70F.

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mmalik
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Re: Lodestar Autoguider new [Re: srosenfraz]
      #5487825 - 10/24/12 11:13 PM

On strange thing I have been noticing is that ST-4 cable that has been (and still IS) working fine with 1MP SSAG, will not work with ST-i. When I connect ST-4 cable that came with ST-i and it guides fine. What's causing this; are ST-4 cables actually different? I thought all ST-4 cables worked the same way (or were essentially wired the same way). Reason I ask this is because SSAG cable is already routed through the mount; plus would like to know why this is so.

By the way, same thing happened to me earlier with Lodestar ST-4 cable. (Although I had to insert a straight through coupler... to connect Lodestar and SSAG cables together, given the proprietary connector (see pic in the post... above) on camera end of the Lodestar cable)


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Re: Lodestar Autoguider new [Re: mmalik]
      #5491692 - 10/27/12 01:10 PM

What's still missing here is a comparison of dark frames with exactly the same exposure times and same stretches.

Most of these programs (and I haven't used PHD much) auto stretch the image for quick display purposes. If there are a few pixels with DN values a LOT higher than the rest of the chip, then you'll see those and the rest of the image will be black. If all the pixels are down in the low DN values, then the stretched image will look noisier.

Years ago, I had a Starlight Xpress HX5 that displayed darks like your loadstar image above (it might even be the same Sony CCD). But the histogram was way on the left, because that ccd had very low dark current - such that I seldom took darks and never took flats.

I doubt there was anything wrong with the loadstar.

-Tim.


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mmalik
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Re: Lodestar Autoguider new [Re: tim53]
      #5494913 - 10/29/12 04:17 PM

Quote:

I doubt there was anything wrong with the loadstar.




I agree; there was nothing wrong with Lodestar when it came to guiding. What I am referring to is physical flaws in the sensor which have no bearing on guiding; Lodestar just had too many physical flaws that's all (to the point where it looks like they are just selling rejects).

If someone was using these cameras of actual imaging (not guiding) then I think sensor physics matters. Guiding is a crude art, NO sensor quality required. My point is different though... at $650 price tag, sensor should be flawless, no column defects or dead pixels, that's all; if someone wanted to use them purely for imaging (not guiding) they should be up to it.

Here is a quote from SBIG "0 column, cluster or dead pixels..." which seems to be true. Lodestar neither makes this claim nor follows it which is fine as well.


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Re: Lodestar Autoguider new [Re: mmalik]
      #5495639 - 10/30/12 12:59 AM

Mike, how the ST-I would stand against Lodestar in sensitivity? I guess when using dedicated scope for guiding, all guiders will do the job, but my interest is using it with OAG with small prisms. I know that ST-I is a step up in sensitivity against Orion SSAG but would like to hear how it perform against Lodestar, if you got the information.

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Re: Lodestar Autoguider new [Re: AstroScience]
      #5497358 - 10/31/12 07:02 AM

Sergio, Lodestar seems to claim guiding sensitivity up to 18 mag.?? while ST-i guarantees 11 mag. If you can find a good Lodestar (i.e., unlike mine which had weird looking oval hot pixels/defects, plus deep column defects), nothing wrong with Lodestar. I just personally like ST-i given the sensor quality with NO defect guarantee. For OAG, I think both will do quite well. On a side note, one difference between the two is ST-4 port style on each. See the port pics I have posted in previous posts; not sure if you have any preference either way.

If you were imaging as well (not just guiding), then I would say go with ST-i instead.

There is significant price variation for Lodestar, from $570 to $650. [I keep wondering why such price variation; unless the discounted ones have more physical defects or are rejects of some sort? Don't know for sure...just guessing from my own experience]

Hope it helps.


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Re: Lodestar Autoguider new [Re: mmalik]
      #5498729 - 10/31/12 11:48 PM

The sony chips tend to have far lower read noise than the kodak chips, in my experience. So I still wonder if you're comparing apples to oranges with those dark frames.

-Tim.


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Re: Lodestar Autoguider new [Re: tim53]
      #5498786 - 11/01/12 12:23 AM

Tim, I am not comparing Sony (Lodestar) with Kodak (ST-i) chip per se. What I am saying is that my Lodestar had elongated hot pixels when they should be discrete. Other Lodestars may be all good; I just didn't find mine up to par.

Here is a comparison of a friend's (Steve's) Lodestar with mine. Notice the discrete hot pixels on Steve’s, while mine are in elongated clusters. This may not have any bearing on guiding but it is a measure of chip quality.

Steve's Lodestar:


Mike's (my) Lodestar:


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