EQ platform with autoguide ?

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HK.Raymond.Tse
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註冊時間: 週一 11 8月, 2003 16:10

EQ platform with autoguide ?

文章 HK.Raymond.Tse » 週日 02 5月, 2004 17:46

Dear all,

I have seen EQ platforms being used for big Dobs in HK but they are only for visual use only.

Some threads in www states that EQ platforms (such as Tom Osypowski's dual axis EQ platform) without any autoguiding can only be used by DSLR for less than 30 sec. So, such EQ platforms are still not enough for astrophotography.

Is it possible to DIY design EQ platform so that it can accept autoguide such as STV or webcam autoguide like Guidedog ?

Chanlunlun
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註冊時間: 週四 09 10月, 2003 21:06

Re: EQ platform with autoguide ?

文章 Chanlunlun » 週一 03 5月, 2004 11:49

HK.Raymond.Tse 寫:Dear all,

I have seen EQ platforms being used for big Dobs in HK but they are only for visual use only.

Some threads in www states that EQ platforms (such as Tom Osypowski's dual axis EQ platform) without any autoguiding can only be used by DSLR for less than 30 sec. So, such EQ platforms are still not enough for astrophotography.

Is it possible to DIY design EQ platform so that it can accept autoguide such as STV or webcam autoguide like Guidedog ?
Dear Raymond,

There surely exist equatorial platform for guiding purpose and this is absoltutely not a new idea. However equatorial platform with guilding capability is not popular mainly due to the fact that it is not as practical as an equatorial mount ( in particular the german type equatorial mount ), especially when we are dealing with long exposure time.

Another draw back is that equatorial platform cannot be attached a precise enough polar scope which makes it difficult to align the pole ( drifting method is very time consuming) . Finally equatorial platform is designed to carry a giant telescope with very long focal length. To take pictures with these equipment required very accurate guiding. It is extremely difficult, if not impossible, to achieve such accuracy in an equatorial platform.

In principle an equatorial platorm for star shooting can be constructed, but the practical value is low.

So we better stick to the proven german equatorial mount.

Best regards

Chan Yuk Lun

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david_kmng
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註冊時間: 週五 11 7月, 2003 00:10
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文章 david_kmng » 週一 03 5月, 2004 12:55

Hi Raymond Tse,

I understand what you mean and actually this is also what I am looking for.

I think at least a simple test can be done, with regard to Mr. Chan's idea. We can start off with a very very low end equatorial mount (such as the so called CG-3 or the one goes with C90 in the old days). We make a rough polar alignment and use the guide dog to do the auto guide.

BTW, I think it is not impossible to use guidedog with an equatorial platform. But a declination correction mechanism is definitly required and it sounds a bit complicated.

Thanks a lot for sharing your experience in guidedog. I checked the website. I think that for my GP at least I should have the SS2k, or buy some relay box that can read LX200 protocol (for example) and wire it to the dual axis controller. Otherwise, I have to stuck to David Ditch's solution.

Regards,
David

HK.Raymond.Tse
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文章 HK.Raymond.Tse » 週一 03 5月, 2004 13:23

Dear Chan Sir,

Thanks for your comments.

My preliminary target is a 14.5 inch F4.3 "small dob" with focal length about 1600mm. Not very long focal length.

10 min exposure under Guidedog is all that I wish to achieve. But I do not know how the dual axis EQ platform can fit in the serial cable from the notebook.

Any plan to upgrade your 14.5 inch dob's EQ platform to dual axis for autoguiding ? I would like to participate in this project if you wish to consider upgrading your existing EQ platform.

Chanlunlun
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註冊時間: 週四 09 10月, 2003 21:06

文章 Chanlunlun » 週二 04 5月, 2004 15:29

HK.Raymond.Tse 寫:Dear Chan Sir,

Thanks for your comments.

My preliminary target is a 14.5 inch F4.3 "small dob" with focal length about 1600mm. Not very long focal length.

10 min exposure under Guidedog is all that I wish to achieve. But I do not know how the dual axis EQ platform can fit in the serial cable from the notebook.

Any plan to upgrade your 14.5 inch dob's EQ platform to dual axis for autoguiding ? I would like to participate in this project if you wish to consider upgrading your existing EQ platform.
Dear Ray,ond,

Unfortunately I regret to inform that at the moment there is no plan for modification of our exusting EQ platform. For one thing it is very difficult to add a declination axis to the platform, which is originally designed as a single axis unit. For another it is unthinkable to couple a ST-4 or equivalent autoguiding unit onto our existing platform.

Hence, for star shooting, as I always insist, we better stick to the german type equatorial mount.

By the way a 14.5 inch Newtonian with photo capability sounds a little bit too heavy in weight. For large scale deep sky shooting I would suggest a C-11, compressed to f/6.3 or f/3.3, taking the advantage that it is relatively light weight and being more versatile.

Best regards

Chan Yuk Lun

HK.Raymond.Tse
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註冊時間: 週一 11 8月, 2003 16:10

文章 HK.Raymond.Tse » 週二 04 5月, 2004 16:58

Dear Chan Sir,

Another option may be a smaller dob 12.5-inch F4.5 but the standard add-on is only azi-alt mount. Field rotation will be an issue for accumulative exposures.

However, I must first sort out how dual axis EQ platform can be controlled by autoguide before any firm decision can be made whether to purchase the dob.

If there is no way to use autoguide on dob for at least 10 min exposure, then I have to stick to GEM for the time being.

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