成功升呢: 首次用LVI autoguide

[cometboy]

搞唔掂QHY5，決定試玩 LVI。經過高人指點後，終於成世人第一次用到autoguide了。雖然50%放大時會見到拉線，但暫時已很心足了。累積了經驗，下次應會更好。

拍攝資料：Maxvision 102 mm (focal length: 700 mm), x0.8 reducer (即實際560 mm), ISO200, 1x 10 min, UHC filter, modified 450D
On Vixen SXW mount, guided by LVI on Wah! 代理的"山寨導星鏡"

[Tinping]

GOOD GOOD GOOD!!! [水草舞]

[willis]

Hi Cometboy!
Congratulation! The focal length ratio of ur guide scope to the main scope is not very good. (i.e. 220mm Vs 560mm). I also have this 山寨 scope. The focuser is not very tough & have flexure. The guiding performance improve a lot after I used another cheap guide scope of 350mm. (Note my main scope is 500mm in focal length). In addition, if u do not change the LVI sensor direction or the scope doesn't pass the Meridian, there is not need to calibrate the LVI even lost star happened. Just load the data. This saves lots of time. Anyway, make good balance of the setup & hang the cables carefully, u can make perfect guiding! By the way, did u buy the special cable for Vixen or ur Vixen is a new version & no need to use the cable?
Anyway, now u know what is evidence.
Clear skies!
Willis

[cometboy]

Hi Willis,

Thanks for your advice. I know the 220 vs 560 ratio is too tough. But I don't have longer guiding scope on hand and it is why I am confident that the tracking result will definitely be better in my next trial. Practically, it is impossible to have the LVI position unchanged after re-aiming new object because I need to swap LVI and eyepiece to find new guiding star, particular when the new object is far away from the old one (even not passing the Meridian). I think that is a trade-off between precise tracking and saving in recalibration time. The dealer said that the cable supplied in new batch should fit most mounts, including my Vixen SXW (which is standard ST-4 size).

To be fair, LVI really has advantages: simple and no notebook required. But the CCD is not sensitive and large enough. I can only use stars brighter than mag 2 to avoid the message of "Star No Found" or "Star Lost". I am worrying that some objects may not have some bright stars nearby. It is a headache to find guiding star under 30 to 40 times magnification, in particular when the star is high up in the sky. Also, the processor is very slow. After finding a guiding star. adjusting exposure can take 2 to 3 min. Then calibration will take another 7 to 10 min. If the manual was better written, users can save a lot of trouble. I can ultimately solve most of my problems only after a detailed conversation with "社長". Any way, I really enjoy the archievements it gave me.

I have some ideas that are helpful for new users: get a bright guiding scope; make a finder for the guiding scope; put the guiding scope on micro-mount which can be moved in wider direction (in order to catch bright stars that might not be close to the object).

[willis]

Hi Willis,

Thanks for your advice. I know the 220 vs 560 ratio is too tough. But I don't have longer guiding scope on hand and it is why I am confident that the tracking result will definitely be better in my next trial. Practically, it is impossible to have the LVI position unchanged after re-aiming new object because I need to swap LVI and eyepiece to find new guiding star, particular when the new object is far away from the old one (even not passing the Meridian). I think that is a trade-off between precise tracking and saving in recalibration time. The dealer said that the cable supplied in new batch should fit most mounts, including my Vixen SXW (which is standard ST-4 size).

To be fair, LVI really has advantages: simple and no notebook required. But the CCD is not sensitive and large enough. I can only use stars brighter than mag 2 to avoid the message of "Star No Found" or "Star Lost". I am worrying that some objects may not have some bright stars nearby. It is a headache to find guiding star under 30 to 40 times magnification, in particular when the star is high up in the sky. Also, the processor is very slow. After finding a guiding star. adjusting exposure can take 2 to 3 min. Then calibration will take another 7 to 10 min. If the manual was better written, users can save a lot of trouble. I can ultimately solve most of my problems only after a detailed conversation with "社長". Any way, I really enjoy the archievements it gave me.

I have some ideas that are helpful for new users: get a bright guiding scope; make a finder for the guiding scope; put the guiding scope on micro-mount which can be moved in wider direction (in order to catch bright stars that might not be close to the object).

“unchanged” mean roughly the same. According to my experience, the change of the angle of the sensor may be less than 20 deg. The LVI will take care of the change. Try & u will see how it work. u can save time.

I have used the山寨 scope since last yr. I found that the effective diameter is smaller than 50mm. If u look at the scope carefully from the objective side, u can see that there is an extended tube inside the scope & that extended tube’s diameter is much smaller than the diameter of the objective. It blocks part of the light. I’ve mention this in my blog last yr:
http://willisao.blogspot.com/2010/02/sm ... r-and.html
Anyway, yes the LVI’s sensor is less sensitive compared with SBIG’s sensor. But according to Taiwan trip experience this summer, a 50mm guide scope (社長Modified it from a 50mm finder scope) with both angle of elevation & angle of panning of about 10 something degree, we can always find guide stars in the sky. See this link:
http://www.astrocafe.hk/viewtopic.php?f=18&t=347
http://www.astrocafe.hk/viewtopic.php?f=20&t=326

Look at these two small guide scopes which are piggybacked on the main scopes. (They are 40mm & 50mm respectively)
http://1.bp.blogspot.com/__8I1Z-euPws/T ... _6297s.jpg

With these small guide scope, we are able to make these:

My photos (My case is even worst; my guide scope is a modified 40mm finder scope):
http://willisao.blogspot.com/2010/07/ha ... -trip.html
http://willisao.blogspot.com/2010/07/un ... ntain.html

社長 photos:
http://www.astrocafe.hk/viewtopic.php?f=17&t=371
http://www.astrocafe.hk/viewtopic.php?f=17&t=372

Of course, if u are using a even bigger, say 60mm or 70mm guide scope, the guiding speed is faster as the exposure time is shorter. But the trade off is that u need to make sure no flexure for bigger & heavier guide scope.
Willis

[David]

I am amazed that you only need one phone call to use LVI successfully!

Congratulations. I know how you feel because I had the same feeling with LVI when I used it myself for the first time: I never knew that guiding is so easy!

[funoooo]

LVI is a very interesting product. I need to take the serious consideration on it.

[Wah!!]

...
I have used the山寨 scope since last yr. I found that the effective diameter is smaller than 50mm. If u look at the scope carefully from the objective side, u can see that there is an extended tube inside the scope & that extended tube’s diameter is much smaller than the diameter of the objective. It blocks part of the light. I’ve mention this in my blog last yr:
http://willisao.blogspot.com/2010/02/sm ... r-and.html
...

I just did a rough observation, and find that the china-made 60mm refractor will have light blocking when using 90 degree diagonal, but won't have (much) light blocking when diagonal is not being used (assuming that the camera sensor is not extremely far behind the 1.25" adaptor).
I remember I have confirmed this with the producer, and I will do a more detail test later.

[willis]

To Wah:
I think the drop off of the light is not the significant issue for my guiding, really for my guiding only. The LVI is able to find guide star with this scope. (I made a typo in my previous post. The diameter should be 60mm instead of 50mm) The main issue should be the focal length of the China made 60mm scope is too short for guiding a scope of 500mm or above. The other problem maybe the flexure. The brackets & screws provided to hold the 60mm scope are not rigid enough. So if one uses the China made 60mm scope for guiding a wide filed scope, say below 400mm, there would be no problem. The key point is able to find a guide star.

To David:
As a novice like me, I don’t even think I can do auto-guiding in one night only. Everything is so repeatable. Therefore I fully understand Cometboy & your feeling that auto-guiding can be Soooo easy!

[Wah!!]

The 2nd generation bracket is much more rigid than the 1st generation, will you consider to buy it?

What is the guide star limit magnitude for a 60mm scope with LVI?

[funoooo]

To Wah:
I think the drop off of the light is not the significant issue for my guiding, really for my guiding only. The LVI is able to find guide star with this scope. (I made a typo in my previous post. The diameter should be 60mm instead of 50mm) The main issue should be the focal length of the China made 60mm scope is too short for guiding a scope of 500mm or above. The other problem maybe the flexure. The brackets & screws provided to hold the 60mm scope are not rigid enough. So if one uses the China made 60mm scope for guiding a wide filed scope, say below 400mm, there would be no problem. The key point is able to find a guide star.

To David:
As a novice like me, I don’t even think I can do auto-guiding in one night only. Everything is so repeatable. Therefore I fully understand Cometboy & your feeling that auto-guiding can be Soooo easy!

Dear all,
How's about to add Balow?
Now Wah's guide scope is focual length 220mm.
If add the X2 barlow, that will be 440.
If add the X3 barlow, that will be 660.
Base on the 1/3 theory, that will be good to guide the C8. (2000mm)
Is it right?

[willis]

The 2nd generation bracket is much more rigid than the 1st generation, will you consider to buy it?

What is the guide star limit magnitude for a 60mm scope with LVI?

I saw ur 2nd generation post. But the focal length is the same & may not good for guiding my 500mm 80ED.
About the limited magnitude for a 60mm scope, I don't know exactly. But according to my limited experience with a 50mm guide scope (It is modified from a 50mm finder scope & a 2X barow), it is always possible to find a guide star around the object u want to image. Well if the sky condition does not allow a 60mm guide scope to find a guide star, I doubt one can do DSI that night.
PS* The main purpose of the China made 60mm scope is birding for me. Grab & GOOO!

[wenjia]

I have used the山寨 scope since last yr. I found that the effective diameter is smaller than 50mm. If u look at the scope carefully from the objective side, u can see that there is an extended tube inside the scope & that extended tube’s diameter is much smaller than the diameter of the objective. It blocks part of the light. I’ve mention this in my blog last yr:
http://willisao.blogspot.com/2010/02/sm ... r-and.html

Willis

hi, Willis
第一代导星镜是存在调焦桶过长，有遮挡的问题
但第二代导星镜舍弃了第一代的调焦座 已经没有这个遮挡口径的问题了

另外LVI的导星性能我觉得不至于比SG4差太多
很多使用SG4的作品 可以做到1：8.2

台湾的饶兄使用60220+SG4 导威信的VC200L（200F9)
加ha滤镜后15分钟的曝光都很完美


导星镜+VC200L


原帖
http://hkastroforum.net/viewtopic.php?p=194994#194994

[willis]

hi, Willis
第一代导星镜是存在调焦桶过长，有遮挡的问题
但第二代导星镜舍弃了第一代的调焦座 已经没有这个遮挡口径的问题了

另外LVI的导星性能我觉得不至于比SG4差太多
很多使用SG4的作品 可以做到1：10

台湾的饶兄使用60220+SG4 导威信的VC200L（200F10)
加ha滤镜后15分钟的曝光都很完美

I have no experience of SG4 and the post here is not comparing LVI & SG4. Cometboy, DAvid & I just shared our views on LVI. In fact & as a matter of fact, due to my limited budget, LVI is my choice & it simply works for me without much learning. I like "plug & play" equipment.

[cometboy]

I found the "山寨導星鏡" (I am using the 2nd version) is not good for LVI because the focusing tube is too long when the CAM is on focus (without diagonal), making flexure a problem. Also, the six-screw design in brackets limits the range of movement of guiding scope . Finally, it is quite difficult to adjust six screws together under 30 to 40 times magnification while keeping a guiding star in the middle of field.