Help with Star Adventurer and Phd2

[Lorenzo]

Hello guys,

I am trying to get the best (longest) guide with Star Adventurer and a refractor 80 / 480 with field flattener 0.8x with Asi 294Mc Pro (2.5" resolution per pixel). Total weight about 4kg (max. payload of Star Adventurer 5kg). With sturdy Eq6 tripod and William Optics base. No problem of stability here.

First of all I tried 2 different guiding scopes:

a) mini guider 30mm f/4 (120mm FL) with Asi 120MMS. 6,5" resolution per pixel;

b) guiding scope 60mm f/4.6 (280mm FL) with Qhy 462C. 2.1" resolution per pixel. (With this guiding scope on my Neq6 I can guide the refractor above, as long as I wish without problems).

I use 1kg counterweight and a ball head carring the guiding scope (20kg payload) to balance perfectly without flexures. No doubt about this topic.

The main thing here to observe, and which surprised me a lot: no difference in terms of better or worse guiding between the 2 scopes! I tried a lot of time, changing their positions, switching them and changing the area of the Sky to be sure. It makes not sense for me but this is what I got.

That said, with this setup (refractor 4kg, 384mm FL f/4.8, Asi 294Mc Pro - no matter the guiding scope for what I wrote above) the best (longest) exposure time I got is 60 seconds. Already at 80 seconds the star are not longer perfectly round, at 90 I can throw the image. But at 60 seconds works fine.

I read a lot in Internet and saw video of users that can get a perfect image with lens like Tamron 150-600 @600 FL for several minutes (3-4). I am far from that!

(I am able to guide with Canon 70-200 @200mm for 5 minutes, stars are good but not perfect. At 3 minutes are perfect).

How to improve the performance? Because many people seems they can. On gear side I think I tried all the possible solutions and positions.

In PHD2 I keep:

"DEC disabled" and "assume DEC is orthogonal to AR" enabled.
Now my question is: in "brain" advanced settings, calibrations, I noticed that there is the parameter "guide speed sidereal" at 0.5x.

I don't know why, but should i change it to 1x? I actually don't know what to set for Star Adventurer.

Usually I keep it at 0.5x because I use that with Neq6 and newton 10".

Maybe I need to change it at 1x and redo the calibration?

Thanks in advance for some advanced hints, mainly because it seems there is room to improve the exposure time, at least reading some forums, and I am sticked at 60" no matter how much I try.

Thanks a lot!

Lorenzo

[Brian Valente]

Hi Lorenzo

you need to upload your guidelogs for us to give you any meaningful feedback

https://openphdguiding.org/getting-help/

Have you asked for details from those people doing longer exposures?

imo i don't think the kinds of questions you are asking around guiding is going to make the biggest difference for you. 

The Star Adventurer is a small and quirky mount. Tracking only in RA (and no DEC) means a lot of your performance will relate to precise polar alignment. 

In addition, it's not a very precise mount with a lot of manufacturer variability, so there are other "how to use" type of tips that may make a big difference. For example, using only with the counterweight pointed directly down (and resetting your pointing by using your ballhead) seems to make a big difference

Have you asked those 

Have you tried reaching out to those people

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Brian Valente

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[marc whitsett]

Have never used the Star Adventurer so disclaimer. Just two thoughts. 

1. Polar alignment? Method and accurate? 

2. Guide speed? Some say that using 1.5-2X tracking is better. I use 1-1.5X for best results depending.

Marc

[Brian Valente]

Marc is your guidespeed really above 1x sidereal? that would cause reversals in RA

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[marc whitsett]

My bad.  Was referencing exposure durations not sidereal tracking. 

Marc

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[Lorenzo]

Thanks to everybody for the help!
Yesterday I tried to guidespeed at 1x, a little bit improved but not such a big difference.

I think, as you said, that the problem is a not so perfect Polar Alignment: I checked with drift method and I got a significant error in DEC (AR was almost perfect).

Next time I will improve that before anything else.
Thanks!