Help with Celestron 8SE

[Lorin Robinson]

New Celestron 8SE owner and not impressed. Alignment is a bitch.  I finally "succeeded" with the three-star align and then the scope would only take me sort of close to where I wanted to go.  Had to adjust manually.  How spot on is alignment supposed to be?  Tracking?  I can't tell from the inadequate instruction manual how to engage tracking once I'm on an object.  The whole exercise was supposed to allow me to do some astrophotography with my Canon 5D and related camera-to-scope attachments.  Finally, I was surprised to learn (I think) that one needs to go through the alignment process for each session.  The "computer" apparently doesn't hold the alignment.  That right?  Again, I can't find any reference in the instruction manual!   If this is the case, it's certainly inconvenient.  Any help or advice will be appreciated.

[iapa]

Entering date and time correctly and accurately - particularly for 'daylight' savings time, and your location; make sure you enter latitude/longitude in the right order.

Once you have picked your first star, the computer builds a 'map' of the sky. When you elect the second star, it may be off, but by manually entering that star, the map is improved, again for the third..

If you do not move the mount from one day to the next, there is a hibernation function that you can use. That will let you power off the mount, and will retained alignment information when you next power back on. On the hand controller, from the main menu, utilities then hibernate.

Moving the mount will invalidate the alignment, whether or not you use the hibernate function. It is only useful if you do not move the mount before you power on the next time.

The 8SE is probably better suited to planetary, lunar or solar (with a solar filter!!!!) photography due to it's long focal length, although I have tried to use the SCT for DSOs (on a different tripod/mount tho').

HTH

 

[usingen1]

Thats not correct I have used it for dso's very successfully  using a 2" diagonal which is essential for photography 

[ronin]

A lot depends on expectations, and I suppose it is best to start out saying that the goto is not going to be the object bang in the center everytime.

Alignment is best done by adding your location, not using the list of options in the  software. So you will need to know your Longitude and Latitude and the timezone that you are in. Not sure if Baja is a specific town/city or an area, have the impression it is an area and a city so cannot suggest values at this time.

3 star alignment can be a problem. One of the corrections determined by 3 star is a bit intolerant, many simply perform the 2 star alignment.

Set the whole thing up as level as you can, find the start position of the sysstem and again set that up as accurate as reasonable. Also do not use Polaris as one of the stars. The software tends to not do well with Polaris, think it is a bit too close to "0", so use something East and West.

One way of putting it all is that during the alignment the scope has to determine the corrections that it needs to apply for the innacuracies of the setup. So the smaller the corrections then the easier it all should be.

When you have successfully done the alignment then goto a nice bright single star, Betelguese, Rigel, Denebola, Aldebaren any thing single and easy. Then center it. After that do a sync action. Now I think it is: Press and hold Esc for about 2 seconds. The scope should then set it's position in memory as pointing at whichever star you selected. The catch here is I am not 100% sure about the Esc button but that is what I seem to recall someone saying.

Reason for this is you have to realise how the thing works:

Make sure the power supply is adaquate, batteries do not last long and any drop in voltage causes problems.

The alignment will need to be done each time unless the scope is on a permantent pier. You just cannot get it set exactly the same the next time.  The scope has to assume that it has changed position/orientation by even a small amount, and for these even 0.25 of a degree change is big. So yes you do the alignment every time.

Others will differ but for astrophotography it is not the best choice of scope. The actual scope has too long a focal length and is termed "slow". Additionally for long exposure astrophotography the mount is Alt/Az and that causes field rotation of an object.

[Flyingfuzz]

Stay with it, alignment gets quicker and quicker the more you do it.

Normally the goto object is within the eyepiece fov after alignment.

What is important is picking the right stars, make sure they are about 90 degrees apart.

It's worth getting to know the 8se as its a great scope.

If you want a very easy life get the Starsense accessory.

[iapa]

6 minutes ago, usingen1 said:

Thats not correct I have used it for dso's very successfully  using a 2" diagonal which is essential for photography 

I said is it 'probably better suited to', not impossible :).

I did not use a diagonal - I kept the camera in line with the optical path.

What did you use as a guide scope to get long exposures? I found a 80mm f5 just a bit short, even when using the 0.63 fr on the 8" SCT, which allowed maybe 240s exposures

To get back to the OP's question tho': after completing the 3 star alignment, I would the do the All Star Polar Alignment, then do another 3 star alignment, to get your accuracy. Often, people will repeat the ASPA a second time.

I cheat - I purchase the Celestron StarSense and the QHY PoleMaster which save ma a lot of time; polar alignment then star alignment completed in under 15 minutes.

[Marky1973]

19 minutes ago, ronin said:

When you have successfully done the alignment then goto a nice bright single star, Betelguese, Rigel, Denebola, Aldebaren any thing single and easy. Then center it. After that do a sync action. Now I think it is: Press and hold Esc for about 2 seconds. The scope should then set it's position in memory as pointing at whichever star you selected. The catch here is I am not 100% sure about the Esc button but that is what I seem to recall someone saying.

Yep, that's bang on Ronin. I do a two star alignment, adjusting each star to centre as described. Then I slew to a brightish star that is close to my intended target (imaging), centre it and then press and hold ESC for about two seconds and the mount sets that as the point from which to slew to the target, based on the previous alignment data. If you are slewing to a target that is not far from that star, I find it usually very accurate. in so far as the target is always on the chip. Once practiced, alignment can be done in a couple of minutes, but it does rely on a good polar alignment which can take a bit longer.

[alanjgreen]

Hi lorin,

try this for starters...

You will find that alignment does get easier after the first couple of nights.

key points are:

- 3 star alignment is the most difficult, try a 2 star alignment to get the hang of it. Make sure the stars you pick are not too close together. They need to be 90 degress minimum (for example: one in the East then the other in the South or West)

- make sure you don't pick a planet or the moon as one of your three stars!

- Make sure your tripod is level and start with the scope pointing dead straight ahead.

- if you want to align on the moon or jupiter then use "solar system align"

 

Tracking rate

Setting the tracking rate is a once only activity, you need to access the handset menu, find "tracking", then set tracking mode = alt az, tracking rate = sidereal ( job done)

 

 

[cloudsweeper]

I would just suggest a little more practice.  Date, time, and location need to be entered accurately, then alignment with two known stars is quick and easy.  

GoTo should then put the target fairly central (using a low power eyepiece), and if you're not sure, this can be checked with a Sky Atlas or app.

As for tracking, I believe it defaults to alt-az mode - but check just in case it is "off".  Tracking rate, sidereal.

It really does become quick and easy after a few runs.

Doug.

 

[Pig]

I find using a higher power eyepiece to centre targets during alignment than you would normally use to observe with gives much better results.

[cloudsweeper]

8 minutes ago, Pig said:

I find using a higher power eyepiece to centre targets during alignment than you would normally use to observe with gives much better results.

For alignment, yes.  Another method is to defocus the alignment object to a large disc for tighter alignment.

Doug.

[MarkJ44]

Agree the 2 star align is much easier, my only other suggestion to improve accuracy is to refine your alignment with each star using something like a 12.5mm reticle EP, I found this helped a lot. Start with the larger EP and then fine tune with the reticle EP.

[Cosmic Geoff]

If the alignment is done properly, a GoTo should end with the desired object within the field of the 25mm eyepiece. This is what you need, and is good enough if the object is identifiable on sight (e.g. a double star).  It represents an error of around 15 minutes of arc or less - not a bad result.

With the C8 SE one can with advantage use the Starsense accessory to eliminate several setup steps, as well as potentially improving the accuracy. Once the Starsense is set up, there is no need to level the tripod, and hence no need to re-attach the OTA/mount to the tripod, or any need to align manually. Setting up can be reduced to little more than hauling the whole rig out of doors and turning it on.  Last night I did not touch the Red Dot finder at all.

Personally, I find it sufficient to place the alignment star in the middle of the 25mm eyepiece field by eye and always make the final approach from the same directions, when aligning manually.

[Grotemobile]

22 hours ago, alanjgreen said:

if you want to align on the moon or jupiter then use "solar system align"

This is all I have ever used. U can then do a sync on the planet , to get it to track

properly. This is set up I use for imaging. Venus is what I use @ the moment. 

[usingen1]

On 2.3.2017 at 09:00, usingen1 said:

Thats not correct I have used it for dso's very successfully  using a 2" diagonal which is essential for photography 

Of course i used  the 8SE on a avx mount not the altaz mount that a SE comes with  8SE + avx is good for 4 min exposures  , the longest i have tried !  pic is with a Canon eos 6D on moonlite  and  feathertouch micro  focusers, yes both of em...

[Lance Bridwell]

Two star alignment works good for me. Some guy on u tube explains why. I also use a feathertouch focuser.

[newbie alert]

On 02/03/2017 at 08:00, usingen1 said:

Thats not correct I have used it for dso's very successfully  using a 2" diagonal which is essential for photography 

Why does a 2 inch diagonal help with dso's

[cloudsweeper]

9 hours ago, newbie alert said:

Why does a 2 inch diagonal help with dso's

2" EPs have a wider field of view, which can be useful for larger DSOs.

Doug.

[newbie alert]

31 minutes ago, cloudsweeper said:

2" EPs have a wider field of view, which can be useful for larger DSOs.

Doug.

Thanks Doug,but if you didnt have the diagonal in place and have the  camera screwed on the back of the tube with a focal reducer then you would have a wider field of view,flat field and running at 6.3 instead of f10..

[BRUN]

dont suppose you want to sell it lol ?

i need something lighter