Meade LPI or DSI as a guidecam?

[John K]

With the dollar at an all record high, I am considering taking the next plunge for deep sky work and purchasing a guidecam to be used with a 12.5" reflector and an off axis guider. This wil mean faint and sometimes oblique looking stars.

Just wondering whether a Meade LPI or DSI will do the job for me?

Is the LPI sensetive enough? Meade claims that it will guide to Mag 10 or should I go that extra bit and get a DSI seeing that I will be using it with an off axis guider?

Is one easier to use than the other?

Look forward to any advice the more experienced imagers on the forumn can offer.

John.

[JohnG]

Hi

I use an LPI as my temporary guidecamera with my field setup, from experience, you need a bright star to guide on, which can be a bit of a pain to find.

My permanant setup uses an ST-4.

I have on order one of these: http://www.ccd-labs.com/Qseries/qguide.htm
which in my opinion will serpass anything the LPI could do and, I am looking to replace my ST-4 with this guider. Whilst not implying that these are the best, I want to replace all the cables that are associated with a guider, this guider allows you to run the ST-4 compatable outlet direct to your autoguider port. Whilst not standalone, you only have one USB 2.0 cable to muck about with and are purported to run at sub pixel resolution.

Whilst I cannot comment on the DSI, I do not like the Meade software, at least with the LPI you need only download the drivers to work with PHD/GuideMaster/GuideDog whereas I believe that the complete Envisage Suit is required for the DSI (not 100% sure of that though).

Other cameras to consider would be a Toucam, Yankee Robotics Trifid, Fishcamp Starfish.

Cheers

JohnG

[JohnH]

John, I would say the LPI is NOT sensitive enough even with the long exposure mods it will swamp with noise above about 2s. Though with a 12.5" and OAG 2s might get you to a reasonably low mag - maybe 8 - if you ever swith to a guidescope it will not be sufficient, btw where did you get the mag 10 figure from? Also the envsiage s'ware is designed to guide meade scopes so if your mount is not LX compatible you will need more tools to fake it, Ezstyles has written up how to do that if you need to got that way (he drives and EQ6 with Envisage/DSI).

Based on my recent struggles with long fl autoguiding I would very strongly suggest a mono camera for guiding, the QGuide looks very promising, DSI pro series is good too.

JohnG you will share your experiances with us won't you - I am seriously thinking of jumping to this OR doing a chip swap on my Orion...

[JohnG]

No problems, my Q Guider is still about 6 weeks away. :)

The longest f/l I guide on is 1312mm so I am not sure how this will affect your guiding situation.

Cheers

JohnG

[John K]

Thanks guys, that's really good info.

JohnG
- I checked out that guidecam, looks good. What do you think will be the limiting magnitude that it will guide at?
- What are your plans for your ST-4? Do you want me to make you an offer for it?

JohnH
- Some very good points. I have a JMI NGT mount with a drive built by Losmandy providing an ST-4 guideport. When you dont use an ST-4 like guider you need relay adaptors, etc etc so it gets really complex. I guess that's another good point of the guider suggested by JohnG
- Mag 10 is what Meade list on their website as the limiting magnitude for the LPI in terms of guiding

I guess one of the biggest issues is the ability of the guider I get to guide on faint stars through the off axis guider and accuracy as I will be guiding at 1600mm (12.5" f/5)

[JohnG]

Hi John

CCD Labs claim the Q Guider will comfortably guide on Mag 12 stars, realistically, I would say possibly Mag 10, your limitation will be the OAG.

You might want to have a look at the screen shots here:

http://www.pbase.com/wjshaheen/root&view=recent

I use a separate guidescope so I am not hindered in any way with what I guide on, I am looking mainly to get rid of the cable tangle and I like the idea of direct output to the autoguider port on my G-11 and GM-8.

At this stage, until I have done some fairly exhaustive work with the Q Guider, the ST-4 will stay put as it is a proven guider, if the Q Guider proves to be it's equal then I will be selling off quite a number of items to fund some other bits. :D

Cheers

JohnG

[EzyStyles]

Hi John. I'm currently using a DSI II to autoguide which seem very accurate as it is a sensitive CCD. I recall even autoguiding with meade DSI that is still good enough. To autoguide a LPI/DSI on non-meade mount such as the EQ6, i have written up a tutorial here:

http://www.ezystyles.com.au/autoguide.html

hope it helps.

[[1ponders]]

If you can stretch the funds a bit futher you might even consider an ATiK 16IC (http://www.telescope-service.com/atik/start/atikstart.html). If we ever get any fine weather up here I'll even try it out.

Here's one of the US stores for comparison price http://www.astrovid.com/prod_details.php?pid=3246


I've used the original DSI for autoguiding with K3CCDtools V3 and it did the job. I use a guidescope though.

[John K]

Thanks guys, I know for a fact that an ST-4 type unit should work with my set up and an OAG as the guy that builds the NGT scopes at JMI uses this set up and recommends it, I just did not count on the ST-4 being discontinued when I bought the scope.

Wanting to avoing a guidescope option at this stage as the scope is on a truss tube, so although it may be possible it will involved re-engineering the telescope and considerable expense.

So I guess the question is which unit will be as sensetive or better than the ST-4?

JohnG - in your best estimate what is the faintest stars that you have guided on with your ST-4 would you say?

Eric - thanks for that great info. Do you know how sensetive a DSI is in terms of guidestars?

Lastly, with all these units, how good are they at guiding on oblique objects which can be the case with OAG's?

[JohnG]

With an ST-4, the fainter the star the better, that said, I normally have the Exposure set to 1 second and the Gain set to 2, with my 80mm guidescope that equates to a guidestar around Mag 8 -9, the ST-4 will quite happily guide on that all night with an intensity of around 20 - 30.

The ST-4 has been out of production since the early 90's but it is still one of the most desired autoguiders around. The ST-4 has now been well and truly superceded by the more modern cameras with USB 2.0 and direct coupling to the guide ports.

I have never used an OAG but I would imagine that if you can get a star on the CCD chip (which is quite small) you "should" be able to guide on it. The ST-4 has a gain of 4 steps and can pull in quite faint stars when set to 4.

Hope that helps a little.

Cheers

JohnG