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Which scope to buy?


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Hi all,

I want to take the plunge and buy my first telescope but need a little advice.

I will mainly be using the scope for imaging.

I have narrowed down my choice to these 3:

Celestron Nexstar 127 SLT

Celestron Nexstar 130 SLT

Skywatcher Skymax 127 SynScan AZ GOTO

I really like the compactness of the two 127s but would the extra 3mm of the 130 be money better spent?

How do the Celestron & Skywatcher 127s compare in build quality, reliability & future proof etc.... ?

I see that in technical specification terms they are almost identical.

Would the 130 make a better imaging scope?

What extras would I require to attach my DSLR to either scope & get imaging straight away?

Are there any pitfalls with the MAK type scopes over the Reflector type scopes?

Any help would be really appreciated

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Imaging what? Are you looking for planetary or DSO imaging as the requirements can be quite different.

Peter

Hi,

yeah, sorry I meant that I would be imaging some of everything really.

I understand that to get true intricate detail in DSO a larger aperture is needed but in time, I may go that way but for now I'll be quite happy imaging the moon & planets, some nebula (Orion for instance) & maybe venture into to some solar.

So the tracking system has to be robust given the human error element aside [emoji6]

Thanks

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I don't know anything about imaging but the NexStar SLT are Newtonian telescopes whereas the Skymax is a Maksutov-Cassegrain. There are differences between the two types which should be taken account of.

Thanks for replying.

I am now a little more confused because I'm looking on FLO at:

http://www.firstlightoptics.com/beginner-telescopes/celestron-nexstar-127-slt.html

and it states this scope is a Maksutov-Cassegrain type the same as the Skywatcher Skymax.

Is this listing incorrect?

Regards..,

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Hi,

Both 127 scopes are Maksutov-Cassegrain with a 1500mm focal length. The 130 slt is a newtonian reflector with a 650mm focal length. This will have a larger field of view.

The Mak-Cass constructions are more suited for lunar and planet observations. They provide better contrast and higher magnifications with the same eyepieces used on the shorter focal length Newtonian.

With 1500mm focal length you would achieve more than twice magnification than with the 650mm with the same eyepiece (1500/650).

Other significant difference are that Mak-Cass take longer time to cooldown and they attract dew much faster than a Newtonians, but collimation stands much better for Mak-Cass and they need much less maintenance than Newtonians. However, collimating a Newtonian is not a difficult job.

In terms of light gathering abilities, there's virtually no difference between 130 and 127.

Anyway, none of the mounts is very suitable for astrophotography since they all are AltAz mounts. You could achieve some results though even for DSO's. There's a topic with images taken without EQ mounts: http://stargazerslounge.com/topic/228101-the-no-eq-dso-challenge/but the way to go for AP is with tracking EQ mounts.

Best regards,

Alex

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If your main interest is planetary imaging then an AltAz mount will be ok but will not be much use for DSO imaging apart from Orion and maybe a few more. If it is planetary imaging you want this can be done with a DSLR but is better with a solar system CCD to get a bigger image scale. DSOs can be imaged with a DSLR but you would need an equitorial mount. You definitely want a GOTO mount for either.

Not easy is it! Think carefully where you want to go.

Peter

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Thanks for replying.

I am now a little more confused because I'm looking on FLO at:http://www.firstlightoptics.com/beginner-telescopes/celestron-nexstar-127-slt.html

and it states this scope is a Maksutov-Cassegrain type the same as the Skywatcher Skymax.

Is this listing incorrect?

Regards..,

Sent from my 6+ using Tapatalk

Thanks for replying.

I am now a little more confused because I'm looking on FLO at:http://www.firstlightoptics.com/beginner-telescopes/celestron-nexstar-127-slt.html

and it states this scope is a Maksutov-Cassegrain type the same as the Skywatcher Skymax.

Is this listing incorrect?

Regards..,

Sent from my 6+ using Tapatalk

Sorry, my bad, that 127 is indeed a Mak. I blame DuckDuckGo for its inadequacies as a search engine lol. I do know that alt-az mounts aren't so good for imaging though, so I agree with the other posters on this. Equatorial mounts have the advantage of being better for imaging as they can track more accurately I believe. The aren't too intuitive for visual though.

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Hi,

yeah, sorry I meant that I would be imaging some of everything really.

I understand that to get true intricate detail in DSO a larger aperture is needed but in time, I may go that way but for now I'll be quite happy imaging the moon & planets, some nebula (Orion for instance) & maybe venture into to some solar.

So the tracking system has to be robust given the human error element aside [emoji6]

Thanks

Sent from my 6+ using Tapatalk

This is not correct. It is, in fact, extremely 'not correct!'  Here are a couple of DS images taken with an 85mm scope.

M42%20WIDE%202FLsV3-L.jpg

M45%20COMPOSITE%20FL-L.jpg

The scopes at which you are looking would be utterly disastrous for deep sky imaging though fine for planetary. For deep sky imaging you need a fast focal ratio. Around F7.5 is the slowest I would contemplate and significantly faster would be better. Exposure time goes as the square of the F ratio so 5 minutes at F5 equals 20 minutes at F10. Ouch!!!

For long exposure DS imaging you just do need an EQ mount. This is not because they are more accurate but because, in an alt-azimuth mount, the image rotates even if it is always perfectly centred. (Orion rises leaning to the east and sets leaning to the west in the N hemisphere. This is the rotation in question.)

Planetary and DS imaging require opposite approaches and it is hard for one scope to do both. The nearest you can get is with a Newt which has a fast natural F ratio for DS and can be Barlowed-up to a long enough FL for planets. (Planets are bright so the very slow F ratio doesn't matter but, boyoh boy, does it ever matter for DS!)

For DS imaging you also need to match your pixel size to the focal length. DSLRs have small pixels so they should be used at short focal lengths. You will probably never get the tracking good enough, or find a steady enough sky, to use a DSLR productively at long focal length.

Olly

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Thanks everyone for your input.

Definitely not easy.

I'm currently using a iOptron SkyTracker for imaging & seem to get reasonable, (not Hubble), images using it.

Just thought that upgrading to a scope and taking advantage of the huge "lens" over my DSLR lens would be a simple upgrade. [emoji53]

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This is not correct. It is, in fact, extremely 'not correct!' Here are a couple of DS images taken with an 85mm scope.

The scopes at which you are looking would be utterly disastrous for deep sky imaging though fine for planetary. For deep sky imaging you need a fast focal ratio. Around F7.5 is the slowest I would contemplate and significantly faster would be better. Exposure time goes as the square of the F ratio so 5 minutes at F5 equals 25 minutes at F10. Ouch!!!

For long exposure DS imaging you just do need an EQ mount. This is not because they are more accurate but because, in an alt-

The end of you post seems to be missing

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This is not correct. It is, in fact, extremely 'not correct!'  Here are a couple of DS images taken with an 85mm scope.

M42%20WIDE%202FLsV3-L.jpg

M45%20COMPOSITE%20FL-L.jpg

The scopes at which you are looking would be utterly disastrous for deep sky imaging though fine for planetary. For deep sky imaging you need a fast focal ratio. Around F7.5 is the slowest I would contemplate and significantly faster would be better. Exposure time goes as the square of the F ratio so 5 minutes at F5 equals 20 minutes at F10. Ouch!!!

For long exposure DS imaging you just do need an EQ mount. This is not because they are more accurate but because, in an alt-azimuth mount, the image rotates even if it is always perfectly centred. (Orion rises leaning to the east and sets leaning to the west in the N hemisphere. This is the rotation in question.)

Planetary and DS imaging require opposite approaches and it is hard for one scope to do both. The nearest you can get is with a Newt which has a fast natural F ratio for DS and can be Barlowed-up to a long enough FL for planets. (Planets are bright so the very slow F ratio doesn't matter but, boyoh boy, does it ever matter for DS!)

For DS imaging you also need to match your pixel size to the focal length. DSLRs have small pixels so they should be used at short focal lengths. You will probably never get the tracking good enough, or find a steady enough sky, to use a DSLR productively at long focal length.

Olly

Lovely images!

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This is not correct. It is, in fact, extremely 'not correct!' Here are a couple of DS images taken with an 85mm scope.

M42%20WIDE%202FLsV3-L.jpg

M45%20COMPOSITE%20FL-L.jpg

The scopes at which you are looking would be utterly disastrous for deep sky imaging though fine for planetary. For deep sky imaging you need a fast focal ratio. Around F7.5 is the slowest I would contemplate and significantly faster would be better. Exposure time goes as the square of the F ratio so 5 minutes at F5 equals 20 minutes at F10. Ouch!!!

For long exposure DS imaging you just do need an EQ mount. This is not because they are more accurate but because, in an alt-azimuth mount, the image rotates even if it is always perfectly centred. (Orion rises leaning to the east and sets leaning to the west in the N hemisphere. This is the rotation in question.)

Planetary and DS imaging require opposite approaches and it is hard for one scope to do both. The nearest you can get is with a Newt which has a fast natural F ratio for DS and can be Barlowed-up to a long enough FL for planets. (Planets are bright so the very slow F ratio doesn't matter but, boyoh boy, does it ever matter for DS!)

For DS imaging you also need to match your pixel size to the focal length. DSLRs have small pixels so they should be used at short focal lengths. You will probably never get the tracking good enough, or find a steady enough sky, to use a DSLR productively at long focal length.

Olly

OK, I see your point concerning my rather crude comment about aperture size but I knew what I meant but just did not write it all down.

A larger aperture would indeed give a brighter image if in both cases the focal length stayed the same, thus creating a lower (faster) focal ratio.

FL/Aperture

I should have been more precise, sorry, my bad.

I see you have now edited the:

Exposure time goes as the square of the F ratio so 5 minutes at F5 equals 25 minutes at F10. Ouch!!!

to

Exposure time goes as the square of the F ratio so 5 minutes at F5 equals 20 minutes at F10. Ouch!!!

Regards..,

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For now I am content to image the moon, planets & some solar in more detail than I currently can and have decided to go for the Celestron Nexstar 127 SLT for that purpose and to further practice the craft without making an initial vast investment.

I can still capture some DSO, albeit not is as finer detail as many of the peeps here, using my iOptron SkyTracker.

Because of work commitments currently I just need to be able to almost grab and go when I do have some spare time and the weather plays ball.

Doing more nebula stuff does interest me but at the moment the investment does not sit well with my limited time that I would be able to use the equipment.

Regards..,

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OK, about to hit the BUY button on the 127SLT but wanted to add a camera adaptor in with the sale.

What exactly do I need to be able to attach my Olympus 4/3 DSLR to this scope?

Regards..,

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If you get the one with the Barlow lens you can always unscrew and remove the lens if you don't want to use it. The Barlow will double the focal length so you get a bigger image scale.

Peter

 Thanks Peter, much appreciated.

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The Celestron Universal Barlow works well, I use the detachable element on mine sometimes.

http://www.firstlightoptics.com/celestron-eyepieces/celestron-2x-universal-125-barlow.html

Celestron%20AstroMaster%20Barlow_zpsya2y

I often thread the element directly into an eyepiece to give a 1.6x magnification rather than the 2x using it conventionally.

LuminosPlusBarlowElement_zpspklz2xvr.jpg

As with this Celestron Luminos. 

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