Digital Sidereal Clock

[Flyhigh7]

I've been looking for a digital Sidereal Clock that I can program in my location and it would always display the current Sidereal time at my zenith. I know based on my location (now) that Sidereal Time is 2 hours behind my current standard time. So at 10PM it will be about 8h sidereal time, but this changes throughout the year. I'm surprised I have not been able to find a clock like this. It seems simple enough. It would be based on Sidereal time and allow a programmable or analog offset that would account for my location and simply keep time based on Star time.

I just think it would be a neat tool for planning the observing sessions and if for nothing else a unique item. Call me lazy or crazy but I think it would be neat to look at during the day when the stars are not out to see what the Sidereal time is. I'm trying to memorize the constellations and the brightest stars with respect to their location to Sidereal time. Then I'll try to memorize the brightest Deep Space objects. I figure if i can do this, I can have a star map in my head.

I admire you guys who have been doing this for a long time and already have a fairly detailed star map in your head.

[Bigzmey]

On somewhat related subject. If your scope can do 1-target alignment, you can align it on Moon when the Moon is out during the day, and then observe bright stars (Rigel, Aldebaran, etc.) through telescope during the day.

[Flyhigh7]

On somewhat related subject. If your scope can do 1-target alignment, you can align it on Moon when the Moon is out during the day, and then observe bright stars (Rigel, Aldebaran, etc.) through telescope during the day.

Thanks. That's a good idea however I am not bringing this Telescope out while the sun is up until I get a sun filter. Last time the WiFi hung it wouldn't stop slewing until I found the power OFF button. LOL I just don't trust this system yet. Didn't get to go out yesterday due to clouds with 25mph winds. I hope to do that tonight.

Also,I removed the Focus motor because I don't like having to scroll through a few menus to make focus adjustments. If they ever have dedicated Focus IN and Focus OUT buttons, I'll put it back on. I was able to stay connected to SkyPortal (indoors) while not aligned for 30 minutes without a problem so I'm hoping for some good WiFi performance outdoors if I get some clear skies tonight.

I still like your idea to negotiate the updated WiFi Head.

[AstroBee]

Also,I removed the Focus motor because I don't like having to scroll through a few menus to make focus adjustments. If they ever have dedicated Focus IN and Focus OUT buttons, I'll put it back on.

There are very few motorized focusers that are visual friendly. You really only need the motor if you are imaging and not near the scope or don't want to vibrate the system while tuning focuing.
For visual, nothing beats the old manual method.

[OzEclipse]

These were more common 30-50 years ago, less so now.

A sidereal day is 23 h 56 min 4.0905s
The difference between siderial time and mean solar time is a factor of 1.00273791.

Some old digital watches and clocks 1980's and 90's had a small potentiometer that could be tweaked to change the rate. The idea being you could tweak it to get perfect solar time. But you could also tweak to get sidereal time. Had to be a battery clock. Plug in electrics work off the frequency of the mains.

A simple way to work out approximate sidereal time in your head, which for the purpose you are stating of wanting to know roughly what is overhead should be good enough, is that sidereal time is 0 hr at local midnight on Sept 21. Add 2 hrs for every month and 30 mins for every week, 4 mins per day, then add the time of day. If your location is off the time meridian, you need to make a correction of 4 degrees per minute for that eg I live in the +10UT time zone, 150E meridian but I live at 148 degrees so I have to correct (148-150)x4mins= subtract 8 mins. If the total is > 24hrs, subtract 24rs to get back in range.

That rough method will usually get you reasonably close(5-10mins) of true sidereal time

So for example, today Feb 23 at 2:24 pm the sidereal time is
Since September 23(last Autumnal equinox)
5 months x 2 hrs.
+ 0 weeks x 30 mins
+ 0 days x 4mins
10hrs 0m
subtract longitude correction
10:08-00:08=10:00
add Local time 14:24
total 24hrs24m
Sidereal time 00hrs 24m (Calculated from above)

Sidereal time 00hrs 28m (Obtained by precise calculation)

__________________________________________________________________

Today being exactly 5 months was a particularly easy example.

Let's try March 5th at 11:42am

Since September 23(last Autumnal equinox)
5 months x 2 hrs.
+ 1 week x 30 mins
+ 4 days x 4mins
10hrs 46m
subtract longitude correction
10:46-00:08=10:38
add Local time 11:42
total 22hrs 20m
Sidereal time 22hrs 20m (Calculated from above)

Sidereal time 22hrs 29m (Obtained by precise calculation)


There are apps for Android and IOS that will spit out sidereal time. You can set a regular clock off the app at the start of your session and it will get behind sidereal by just 10s per hr. If daylight savings time in in force, you need to correct for that as well. We have DST here at present and I have invisibly corrected for it so as not to complicate it further.

Joe

[KathyNS]

I had an old mechanical travel alarm clock that ran 4 minutes fast per day. Rather than fiddle with the adjustment, I labelled it as a sidereal time clock.

Interestingly, because the RA setting circle on my C-90's fork mount is driven by the tracking motor, it has a sidereal time index. So, I can set my alarm clock to sidereal time before I leave the house, then use it to set the RA setting circle on the mount. I can immediately use it for finding objects without having to centre a known star and look up its coordinates of first.

[Flyhigh7]

Thank you all for the very interesting and informative replies!

[JayTee]

If you download the app "Nightshift" (it's free) using the menu you can select the astronomical clock and it has all the info you need. Plus, it is a pretty cool "astro" app.

Here's a link: https://play.google.com/store/apps/deta ... nightshift

Cheers,

[Flyhigh7]

If you download the app "Nightshift" (it's free) using the menu you can select the astronomical clock and it has all the info you need. Plus, it is a pretty cool "astro" app.

Thanks JayTee. This looks like an excellent App but how can I can't get it to my iPhone if it's not in the Apple Store? Is this for IOS or Android or Both?

[OzEclipse]

If you download the app "Nightshift" (it's free) using the menu you can select the astronomical clock and it has all the info you need. Plus, it is a pretty cool "astro" app.

Thanks JayTee. This looks like an excellent App but how can I can't get it to my iPhone if it's not in the Apple Store? Is this for IOS or Android or Both?

Apple Store has an app, "LST Clock."
Joe

[Flyhigh7]

Apple Store has an app, "LST Clock."
Joe

Thanks Joe. I'm currently upgrading my IOS to 15 to get this clock.

[JayTee]

Unfortunately, I just learned that Nightshift for Android is not the same app as Nightshift for iOS. Sorry about that.

[Flyhigh7]

Apple Store has an app, "LST Clock."
Joe

I had used up all my fast download time so it took 2 days to download the ios upgrade I needed for LST Clock but that is finally done and I have this cool little app now. Thanks for the tip Joe. I like that you can have multiple locations (not that I'm ready to start lugging this beast of a telescope around).

[OzEclipse]

Apple Store has an app, "LST Clock."
Joe

I had used up all my fast download time so it took 2 days to download the ios upgrade I needed for LST Clock but that is finally done and I have this cool little app now. Thanks for the tip Joe. I like that you can have multiple locations (not that I'm ready to start lugging this beast of a telescope around).

Glad that works for you. After that post, I created an excel spreadsheet that worked out LST to within a few minutes accuracy. The mental arithmetic method I described was how I did it back in the 80’s before smart phones and laptop computers.
Joe

[Flyhigh7]

Glad that works for you. After that post, I created an excel spreadsheet that worked out LST to within a few minutes accuracy.

Don't ya just love Excel!. I used to use Visual Basic to program Excel to produce my companies' Operations Failure Rate and Expense Tracking reports. VBA for Excel is fun!

[Flyhigh7]

Update on my WiFi problems:
I am very impressed with Celestron Tech support as they have been very responsive to me in a timely manner and they know what they are doing. When you call Celestron support you actually get Technicians that work at and for Celestron instead of some third party company located on the other end of the world. I'm happy to report they are honoring my request to send me a WiFi Module which should have a stronger WiFi radio in it than the one in my mount. I have clouds in my area for the next few days so I won't be hunting stuff soon but I thank you all for your help.

[OzEclipse]

Glad that works for you. After that post, I created an excel spreadsheet that worked out LST to within a few minutes accuracy.

Don't ya just love Excel!. I used to use Visual Basic to program Excel to produce my companies' Operations Failure Rate and Expense Tracking reports. VBA for Excel is fun!

Well, if you love excel, FWIW, here is the excel spreadsheet. It's not fancy, just something I threw together after I answered your first post to see if I could remember how to do it without a reference. You need to enter the date of the previous autumnal equinox.

Sidereal Time Calculator.zip

(8.44 KiB) Downloaded 10 times

Cheers
Joe

[Flyhigh7]

Good job OzEclipse. Nice little spreadsheet. Thanks.

[billywjackson]

This doesn't help the IOS people, but there is an app for android called Astro Clock. Gives local. true solar, and sidereal times. Also sun, moo , and planet info.

Clear skies!

[Graeme1858]

This doesn't help the IOS people, but there is an app for android called Astro Clock. Gives local. true solar, and sidereal times. Also sun, moo , and planet info.

Clear skies!

Cheers for that.

App downloaded.

Graeme