14 replies to this topic

[MarMax]

I'm going to try a Celestron 80mm (600mm FL) guidescope with my reduced C11 (1760mm FL) and will also try a Player One Uranus-M (585) as the guide camera. The guidescope/camera combination has a 1.0° x 0.6° FOV and comes in at 1" resolution. My typical FWHM range is 3.5 to 5.0. I'm using PHD2 for guiding and a Losmandy G11G mount.

 

I'm only doing EAA so please stay focused on this kit. I'm not interested in OAG feedback.

 

Should I run the camera Bin2?

[Ben Diss]

No.

 

Assuming a 3.76um pixel size of your main imaging camera, you'll be imaging at 0.4 arc-sec/pixel on the Edge binning 1x1. I'd probably just bin 2x2 on the main camera for 0.79 arc-sec/pixel.  On the guide camera, you'll be imaging at 1.0 arc-sec/pixel when binned 1x1. That's a good ratio.

 

This page can help you do this math: https://astronomy.to...ope_suitability

[MarMax]

No.

 

Assuming a 3.76um pixel size of your main imaging camera, you'll be imaging at 0.4 arc-sec/pixel on the Edge binning 1x1. I'd probably just bin 2x2 on the main camera for 0.79 arc-sec/pixel.  On the guide camera, you'll be imaging at 1.0 arc-sec/pixel when binned 1x1. That's a good ratio.

 

This page can help you do this math: https://astronomy.to...ope_suitability

Thanks for the link. I use the site all the time for the other calculators but not the guidescope suitability calculator. There are a lot of different opinions on the best ratio. I'm using a 533MM as the main camera.

[Sacred Heart]

Mike,

 

Depending on the target, seeing you may want to go with binning the main camera at 3 x 3 for a 1.2 image scale.  Again, depending on the night.

 

Joe

[jml79]

I have seen both this thread and your posts in the EAA forum "What did I do with my EAA Rig" and I don't think your issue is with the guide scope and camera. I have 3 rigs that can maintain 0.6-0.8 with a 30mm guidescope and a 462m sensor and 2 of those rigs do much better (as low as 0.3) with longer focal lengths like your 72ED. Either something is up with the mount or PHD2. I just don't know what or which yet. I would stick with the 72ED for now and any of your 2.9um sensors and concentrate on the mount and software.

[MarMax]

I have seen both this thread and your posts in the EAA forum "What did I do with my EAA Rig" and I don't think your issue is with the guide scope and camera. I have 3 rigs that can maintain 0.6-0.8 with a 30mm guidescope and a 462m sensor and 2 of those rigs do much better (as low as 0.3) with longer focal lengths like your 72ED. Either something is up with the mount or PHD2. I just don't know what or which yet. I would stick with the 72ED for now and any of your 2.9um sensors and concentrate on the mount and software.

Yep, I'd have to agree. My 80mm (600mm FL) experiment failed and it's most likely operator incompetence. My knowledge of PHD2 is less than a thimble full and the AM5 with any payload and a 50mm guidescope guides at 0.5 consistently. I've seen a few nights with the C11 at 0.8 but most of the time the G11G is all over the place.

 

It would be nice if there was a list that covered "every" PHD2 setting for a C11/G11G kit. All the PHD2 info I've surfed up is spotty and incomplete. I'm going to stick with the AT72 since it's optically good and very light. I can use either a 178MM or 585MM camera. And there is still a lot of discussion regarding L6 with the Gemini2. I'm up to the latest with updates but have no clue what to change . . . yet.

 

The 80mm experiment was only $75 so no loss other than my time. I should be able to re-home it easily.

[Sacred Heart]

Yep, I'd have to agree. My 80mm (600mm FL) experiment failed and it's most likely operator incompetence. My knowledge of PHD2 is less than a thimble full and the AM5 with any payload and a 50mm guidescope guides at 0.5 consistently. I've seen a few nights with the C11 at 0.8 but most of the time the G11G is all over the place.

 

It would be nice if there was a list that covered "every" PHD2 setting for a C11/G11G kit. All the PHD2 info I've surfed up is spotty and incomplete. I'm going to stick with the AT72 since it's optically good and very light. I can use either a 178MM or 585MM camera. And there is still a lot of discussion regarding L6 with the Gemini2. I'm up to the latest with updates but have no clue what to change . . . yet.

 

The 80mm experiment was only $75 so no loss other than my time. I should be able to re-home it easily.

Mike,

 

OTA is balanced in Dec and RA. with whatever guide scope you are using.  Reasonably close. Pa is Good, very good?? What do you use for PA??  I use Sharpcap.  For me, I used to own a G11T, the trick to polar aligning a Losmandy mount is to loosen both side for RA adjustment then snug it up. you want to feel a little tension when moving the RA. Also, lock both sides at same time. Minimizes movement.  With PA close, within 30 arc seconds, and a good pointing model, you should be set to calibrate PHD2.

 

My neighbor has the mount now, and it was not upgraded to level 6.

 

In PHD2 make sure you guide scope focal length is set correctly,   Calibrate near equator and meridian.  If guiding is bad, not normal, run a guide assistant.  5 - 10 minutes, see what it suggests and apply.  I don't have any specific numbers to tell you.

 

That's all I can suggest,   Joe

 

Maybe the guru's on the Losmandy groups io can help.

[MarMax]

Thank you Joe.  Good information and I do use SharpCap for polar alignment and always set to "Excellent". Last night the PA was actually dead on. I'll start from scratch again with the AT72 and calibrate and run the assistant. The mount is balanced both ways but the total kit is probably close to 45 pounds.

 

One of the mysteries to me with the G11G is backlash and how to account for it.

 

This is some of the notes I've saved from things I've read about PHD2 and the G11G.

 

>Set TVC to zero (0) for the mount. You want PHD2 to
handle all backlash compensation. TVC=0 means the
mount backlash compensation is turned OFF.

 

>Try 3 second exposures (I've been using 2 seconds and tried 2.5 and things got worse).

 

>Run Guiding Assistant (GA) for at least 6 minutes. Accept the
GA recommendations for DEC and RA minimum move.

 

>The default target box of 15x15 pixels is too small.
Set it to 50x50 (maximum)

 

>Force Calibration every night (Shift-Click); must be
within 10 degress of the celestial equator (Dec=0)
for calibration.

 

>Always do a NORTH bump before starting calibration (I've not been doing this).

 

>On the history graph turn on (select) CORRECTIONS and
TREND LINES; good trend lines should be horizontal

 

>Set aggression at 55-70.

 

>Leave MAX move at 2,500ms and set MIN move to 0.15.

 

>Don't trust declination correction in PHD2 (leave off).

[rgsalinger]

This is the DSO imaging forum. If you are doing EAA, then you should post over there. Whether you want to hear it or not, you will not get very good results if you use that rig and have to take 3-4 minute exposures. It's not going to be a PHD issue. I've use an 800mm guide scope on an AP1600AEL with a 2.8 meter scope and about 1/3 of the images had to be chucked. That was the last time I tried to use a guide scope with an SCT and long exposures. It's simply a matter of how SCT's are made. 

[jml79]

This is the DSO imaging forum. If you are doing EAA, then you should post over there. Whether you want to hear it or not, you will not get very good results if you use that rig and have to take 3-4 minute exposures. It's not going to be a PHD issue. I've use an 800mm guide scope on an AP1600AEL with a 2.8 meter scope and about 1/3 of the images had to be chucked. That was the last time I tried to use a guide scope with an SCT and long exposures. It's simply a matter of how SCT's are made. 

Normally I would agree but being active in both forums, very few EAA imagers even guide let alone try for sub arc second guiding. If we forget for a second that this is a C11 that everyone of us would tell him to use an OAG and large sensor guide camera to get rid of flex and mirror flop issues and just treat it as trying to get a mount to guide well with a large refractor then we are likely much more experienced here to help than most in the EAA forum. His goal is a well guiding mount and then shortish subs to account for flex and mirror flop. Nothing radical really. Lets help get the mount guiding like it can and then the OP will have to decide how he wants to deal with the inevitable other issues.

[MarMax]

rgsalinger> I understand your desire to not have to deal with questions from an EAAer. Unfortunately as jml79 says, there is really no other place to go since most doing EAA don't bother with guiding. Also, with EAA the guidescope is an important piece of kit as it serves as an electronic finder for times you run an SCT at f/10 (when plate solving can become difficult).

 

After swapping the AT72EDII back as the guidescope I started from scratch again with the PHD2 wizard. I ran a calibration and was guiding early this morning at a bit under 0.8 which seems to be about the best you get with a G11G.

 

I posted up PHD2 screen grabs in another topic here.

 

My workflow is very consistent regardless of the guidescope used so understanding what is right from wrong is difficult. Hopefully over time I can gather more information from successful users of C11/G11G kits running PHD2. There are a lot of parameters that can be adjusted and minimal information on optimum settings for my kit.

[rgsalinger]

rgsalinger> I understand your desire to not have to deal with questions from an EAAer. Unfortunately as jml79 says, there is really no other place to go since most doing EAA don't bother with guiding. Also, with EAA the guidescope is an important piece of kit as it serves as an electronic finder for times you run an SCT at f/10 (when plate solving can become difficult).

 

After swapping the AT72EDII back as the guidescope I started from scratch again with the PHD2 wizard. I ran a calibration and was guiding early this morning at a bit under 0.8 which seems to be about the best you get with a G11G.

 

I posted up PHD2 screen grabs in another topic here.

 

My workflow is very consistent regardless of the guidescope used so understanding what is right from wrong is difficult. Hopefully over time I can gather more information from successful users of C11/G11G kits running PHD2. There are a lot of parameters that can be adjusted and minimal information on optimum settings for my kit.

Sorry, is the OP planning to do long exposure DSO imaging or just short exposures "like" what folks do over on the EAA forum? My thought was to warn about using guide scopes with SCT's or other long focal length scopes when the subs are more than 30 seconds (say) long  If that's off topic, then apologies.

 

As far as platesolving is concerned I've learned that PWI3 is vastly superior to ASTAP for long focal lengths with small FOV's. I suspect that the prevalence of ASTAP amongst imagers may be leading people astray. (Has ASTAP been improved?) That was exactly my experience.

[MarMax]

Sorry, is the OP planning to do long exposure DSO imaging or just short exposures "like" what folks do over on the EAA forum? My thought was to warn about using guide scopes with SCT's or other long focal length scopes when the subs are more than 30 seconds (say) long  If that's off topic, then apologies.

 

As far as platesolving is concerned I've learned that PWI3 is vastly superior to ASTAP for long focal lengths with small FOV's. I suspect that the prevalence of ASTAP amongst imagers may be leading people astray. (Has ASTAP been improved?) That was exactly my experience.

My desire with guiding an EAA kit is to be able to take subs up to 2 minutes, so 30 seconds, 1 minute and 2 minutes. IMO long exposures are those greater than 2 minutes. I'm using SharpCap and the 0.25" database for plate solving, which seems to work well but can become tricky when running the scope at f/10 with a smallish (less than 4/3) sensor.

 

I don't find your responses to be off topic, it was just surprising to hear you suggest that I go back and play in the EAA sandbox. I've come to expect this type of feedback in the planetary imaging forum but not in BDSI or EDSI.

[rgsalinger]

I never meant to suggest that you should go back to the sandbox!!!

 

I just meant that I've seen way too many examples over the years of people taking exposures of more than 30 seconds at that focal length and getting mediocre to useless results much of the time using a C11, even with the best possible mount. It's also a bit subjective when it comes to star shapes. And, these days there are tools to fix them up. Just realize if it happens that you've also blurring the DSO itself. 

 

Rgrds-Ross

[MarMax]

Thanks Ross, very true that it's difficult running a C11 with a guidescope. Another thing with the EAA forum is you can't post-process images so fixing star shapes is not allowed. It would be much simpler to run unguided and fix the stars in post.

 

If anyone has more PHD2 C11/G11G tips beyond what's in Post #8 please chime in. The AT72EDII / 178MM combo seems to be working at around 0.8" but I'd still like to keep optimizing.