About NexStar 8-SE

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willis
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About NexStar 8-SE

文章 willis » 週日 15 2月, 2009 22:59

1. Can NexStar 8-SE used for long exposure?
2. Is the NexStar 8-SE's optical tube is the same as C8 OTA?
3. Can other telescope, say a 80mm refractor, be mounted on NexStar's mount?
Many thanks!

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David
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Re: About NexStar 8-SE

文章 David » 週一 16 2月, 2009 12:27

willis 寫:1. Can NexStar 8-SE used for long exposure?
2. Is the NexStar 8-SE's optical tube is the same as C8 OTA?
3. Can other telescope, say a 80mm refractor, be mounted on NexStar's mount?
Many thanks!
1. Long exposure requires equatorial mount, not fork mount used in NexStar series.
2. Yes
3. Don't know about the last question if no modification is required. But I guess some DIY can always enable you to do so.

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willis
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Re: About NexStar 8-SE

文章 willis » 週一 16 2月, 2009 16:27

David 寫:
willis 寫:1. Can NexStar 8-SE used for long exposure?
2. Is the NexStar 8-SE's optical tube is the same as C8 OTA?
3. Can other telescope, say a 80mm refractor, be mounted on NexStar's mount?
Many thanks!
1. Long exposure requires equatorial mount, not fork mount used in NexStar series.
2. Yes
3. Don't know about the last question if no modification is required. But I guess some DIY can always enable you to do so.
Thanks David!
What about the C8-GOTO?
http://www.scopehouse.com/Telescope_4.htm
But it must be very expensive. :(

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David
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Re: About NexStar 8-SE

文章 David » 週一 16 2月, 2009 17:01

willis 寫: What about the C8-GOTO?
http://www.scopehouse.com/Telescope_4.htm
But it must be very expensive. :(
It has an equatorial mount, so it allows long exposure. The whole set should be just a bit over $10000.

But due to the long focal length of C8, guiding is needed and I do not recommend this for beginners.

If you just want to GOTO mount, there are other choices available, such as Meade LXD75 or Skywatcher HEQ5Pro. Both can mount C8 with no modifications. So you can buy the scope and the mount separately.

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alget
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文章 alget » 週一 16 2月, 2009 17:08

Off-topic:
http://forum.hkas.org.hk/viewthread.php ... a=page%3D1

Don't expect too much to the telescope......

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willis
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Re: About NexStar 8-SE

文章 willis » 週一 16 2月, 2009 17:50

David 寫:
willis 寫: What about the C8-GOTO?
http://www.scopehouse.com/Telescope_4.htm
But it must be very expensive. :(
It has an equatorial mount, so it allows long exposure. The whole set should be just a bit over $10000.

But due to the long focal length of C8, guiding is needed and I do not recommend this for beginners.

If you just want to GOTO mount, there are other choices available, such as Meade LXD75 or Skywatcher HEQ5Pro. Both can mount C8 with no modifications. So you can buy the scope and the mount separately.
Thanks David!
Is the mount u used last time is HEQ5Pro? If yes, it is a very strong mount :D & very heavy :cry: Just from the photos, the HEQ5Pro is heavier than LXD75 mount.
u know I am kind of new, I found many people use Celestron, say C6, C8, C.... I guess it must be good in some ways :wink: (At least the performance price ratio is good :wink: ) BTW, what it mean by guiding?

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willis
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文章 willis » 週一 16 2月, 2009 17:51

alget 寫:Off-topic:
http://forum.hkas.org.hk/viewthread.php ... a=page%3D1

Don't expect too much to the telescope......
Thanks for telling. This why I need to ask more. :roll:

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David
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Re: About NexStar 8-SE

文章 David » 週一 16 2月, 2009 19:23

willis 寫:Is the mount u used last time is HEQ5Pro? If yes, it is a very strong mount :D & very heavy :cry: Just from the photos, the HEQ5Pro is heavier than LXD75 mount.
u know I am kind of new, I found many people use Celestron, say C6, C8, C.... I guess it must be good in some ways :wink: (At least the performance price ratio is good :wink: ) BTW, what it mean by guiding?
Yes, HEQ5pro was the one you saw last time. It was slightly heavier than LXD but not much.

People usually buy C6 and C8 because such optical design (Schmidt Cassegrain) makes the tube short, thus very portable. 6 inch and 8 inch give you good light collecting power. There aren't many companies which sell scopes with such design and at such aperture and at such good price.

What is guiding? Basically, if you shoot with long exposure, your equatorial mount has to follow the stars PERFECTLY to avoid a star becoming a line in your photo. In reality, it is extremely difficult to achieve such perfection unless you spend a lot of time positioning your mount perfectly.

So what we do is that we mount another scope on the same mount with an eyepiece in it, and make it point towards a star. You then look into this star and adjust with the use the controller of the mount to ensure that this star remains in the centre all the time. (Without you making corrections, this star will gradually move away from the centre.) This process is known as guiding. The telescope for this purpose is usually a refractor and is known as a 'guidescope'.

You can see some pictures of mount with many scopes and cameras on it in this link:
http://forum.hkas.org.hk/viewthread.php ... age=5#zoom
Usually, one of the telescopes on the mount is for guiding purpose.

It is possible to do guiding without using your eye and you making corrections manually. You can do this by a computer, webcam, and with some appropriate softwares. This is known as 'autoguiding'.

Guiding is recommended for long exposures and long focal length photography. Otherwise, you can usually get away with it. To give you some idea, for f=500mm, it is possible to do exposure of around 2-3 minutes without guiding. For C8's 2000mm with no guiding, you can only have less than 1 minute exposure in most cases.

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funoooo
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文章 funoooo » 週二 17 2月, 2009 11:38

LX-75 is very commend EQ mount in Hong Kong, you will find a lot of support from the other starizer.
HEQ5 is a little bit heavy, and less starizer to use in Hong Kong. However, the quality is better than LX-75, base on the other starizer comment. Now the HEQ5 is under promotion. It seems under HK$5000. Thus, I think you need to think about it' which one is your best EQ mount. You are lucky you know DAVID, so you can get the support from him. Furthermore, both of them are made in China.

For the telescope, there is a very high comment for the C8. Thus, that will be a good choice. However, for the astro-photo, I think you need to pay more attention to EQ, instead of telescope. The EQ is a critiria factor to get teh nice photo. At the beginning, you just get the fair scope, but the nice EQ. You are o.k. to get the deep sky objects. Furthermore, you want to take the nice photo, you suppose to looking for refraction lens. Although the object len is not large, (normal it's around 4") however, it can give you very sharp nice image. Thus, a lot of starizer prefer to use the refraction teelescope to take photo.

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willis
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Re: About NexStar 8-SE

文章 willis » 週二 17 2月, 2009 17:59

David 寫:
willis 寫:Is the mount u used last time is HEQ5Pro? If yes, it is a very strong mount :D & very heavy :cry: Just from the photos, the HEQ5Pro is heavier than LXD75 mount.
u know I am kind of new, I found many people use Celestron, say C6, C8, C.... I guess it must be good in some ways :wink: (At least the performance price ratio is good :wink: ) BTW, what it mean by guiding?
Yes, HEQ5pro was the one you saw last time. It was slightly heavier than LXD but not much.

People usually buy C6 and C8 because such optical design (Schmidt Cassegrain) makes the tube short, thus very portable. 6 inch and 8 inch give you good light collecting power. There aren't many companies which sell scopes with such design and at such aperture and at such good price.

What is guiding? Basically, if you shoot with long exposure, your equatorial mount has to follow the stars PERFECTLY to avoid a star becoming a line in your photo. In reality, it is extremely difficult to achieve such perfection unless you spend a lot of time positioning your mount perfectly.

So what we do is that we mount another scope on the same mount with an eyepiece in it, and make it point towards a star. You then look into this star and adjust with the use the controller of the mount to ensure that this star remains in the centre all the time. (Without you making corrections, this star will gradually move away from the centre.) This process is known as guiding. The telescope for this purpose is usually a refractor and is known as a 'guidescope'.

You can see some pictures of mount with many scopes and cameras on it in this link:
http://forum.hkas.org.hk/viewthread.php ... age=5#zoom
Usually, one of the telescopes on the mount is for guiding purpose.

It is possible to do guiding without using your eye and you making corrections manually. You can do this by a computer, webcam, and with some appropriate softwares. This is known as 'autoguiding'.

Guiding is recommended for long exposures and long focal length photography. Otherwise, you can usually get away with it. To give you some idea, for f=500mm, it is possible to do exposure of around 2-3 minutes without guiding. For C8's 2000mm with no guiding, you can only have less than 1 minute exposure in most cases.
Thanks David!
This is a very informative reply. Long focal length astrophotography is a long way to go! BTW, As u mentioned the Meade LXD75, I try to do some searches about it. While I was looking at the LXD75 mount, I found there is a series of Meade called ACF. It is not Schmidt-Cassegrain, but Advanced Coma Free. The ACF is being used in LX200-ACF and LX90-ACF series. But these two series use fork mount. However there is one ACF scope in the LXD75 series, LDX-75 ACF-8AT. It shares the same tube/scope as LX200-ACF 8” and LX90-ACF8”. This drawn my attention & I do some searches on it. The reviews are quite good. It seems the optical design of ACF outsmarts SC. Do u have any experience about the ACF scopes? Any comment?
Regards,
Willis

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willis
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文章 willis » 週二 17 2月, 2009 18:07

funoooo 寫:LX-75 is very commend EQ mount in Hong Kong, you will find a lot of support from the other starizer.
HEQ5 is a little bit heavy, and less starizer to use in Hong Kong. However, the quality is better than LX-75, base on the other starizer comment. Now the HEQ5 is under promotion. It seems under HK$5000. Thus, I think you need to think about it' which one is your best EQ mount. You are lucky you know DAVID, so you can get the support from him. Furthermore, both of them are made in China.

For the telescope, there is a very high comment for the C8. Thus, that will be a good choice. However, for the astro-photo, I think you need to pay more attention to EQ, instead of telescope. The EQ is a critiria factor to get teh nice photo. At the beginning, you just get the fair scope, but the nice EQ. You are o.k. to get the deep sky objects. Furthermore, you want to take the nice photo, you suppose to looking for refraction lens. Although the object len is not large, (normal it's around 4") however, it can give you very sharp nice image. Thus, a lot of starizer prefer to use the refraction teelescope to take photo.
Thanks funoooo!
Yes! I am lucky that David shares lots of experience with me! :D BTW, the weight of the equipment is important. The lighter they are, the greater the temptation! It just tempts u to use it more! :twisted: Agree with u! Refractors give sharp & high contrast images. That's why I will start with a refractor & then a catadioptric scope later. Do u have any suggestions? :?:
Regards

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funoooo
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文章 funoooo » 週二 17 2月, 2009 19:05

I just get the news. The skywatcher EQ3pro is lauched. They said that is as accuracy as EQ6 :shock: . and very light weight. That will be great for traveling. (Please read my the other post. :lol:) It will be the other good choice. I have no idea where to sell it in Hong Kong. You need to check to Hong Kong suppliers. They may have it.

http://www.hkastroforum.net/viewtopic.p ... 172#133172

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David
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文章 David » 週二 17 2月, 2009 21:08

funoooo 寫:I just get the news. The skywatcher EQ3pro is lauched. They said that is as accuracy as EQ6 :shock: . and very light weight. That will be great for traveling. (Please read my the other post. :lol:) It will be the other good choice. I have no idea where to sell it in Hong Kong. You need to check to Hong Kong suppliers. They may have it.

http://www.hkastroforum.net/viewtopic.p ... 172#133172
Seems to be a good mount if one wants to mount a C8 or 8" ACF. You may read other's comment in another thread.

But there is always some compromise between steadiness and size of the mount. May be this small mount is good enough for visual use, and bigger mount is still better for photography.....Just a guess because haven't used it before.
最後由 David 於 週二 17 2月, 2009 21:39 編輯,總共編輯了 3 次。

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David
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Re: About NexStar 8-SE

文章 David » 週二 17 2月, 2009 21:20

willis 寫:BTW, As u mentioned the Meade LXD75, I try to do some searches about it. While I was looking at the LXD75 mount, I found there is a series of Meade called ACF. It is not Schmidt-Cassegrain, but Advanced Coma Free. The ACF is being used in LX200-ACF and LX90-ACF series. But these two series use fork mount. However there is one ACF scope in the LXD75 series, LDX-75 ACF-8AT. It shares the same tube/scope as LX200-ACF 8” and LX90-ACF8”. This drawn my attention & I do some searches on it. The reviews are quite good. It seems the optical design of ACF outsmarts SC. Do u have any experience about the ACF scopes? Any comment?
I have no experience with this scope, and so you may need to wait for other user's opinion. My guess (may be wrong) is that the difference is not really that noticeable visually unless one really looks carefully for the difference. May be the effect on photography with larger CMOS is more significant. i.e. hardly any effect on planetary imaging with much smaller CMOS.

With C8 or 8" ACF, other factors may be more important in order to give a good image: good atmospheric seeing (i.e. how turbulent the atmosphere is) and whether you have collimated your scope accurately before use. My guess is that whether the scope is ACF or not is not that crucial. So if one already has C8, it is not worth switching to 8"ACF.

However, since you are just starting your hobby, I am sure that you won't be disappointed with either C8 or 8"ACF. It is just the matter of cost.

I have both LXD75 and also HEQ5Pro. You are welcome to contact me if you want to try them.

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willis
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文章 willis » 週三 18 2月, 2009 10:57

funoooo 寫:I just get the news. The skywatcher EQ3pro is lauched. They said that is as accuracy as EQ6 :shock: . and very light weight. That will be great for traveling. (Please read my the other post. :lol:) It will be the other good choice. I have no idea where to sell it in Hong Kong. You need to check to Hong Kong suppliers. They may have it.

http://www.hkastroforum.net/viewtopic.p ... 172#133172
Dear funooo,
Thanks for telling! BTW, what mount u are using? Any comment? Apart from Skywatcher & Meade's mount, what about this one?
http://www.celestron.com/c3/product.php ... ProdID=541
This a Celeston's set lunch, C8 + Computerized Mount . Do u have any experience about it? :roll:
Regards,
Willis

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